It is true that increased throughput yields a mana efficiency for all throughput stats except for the most part Haste. Now the point I am trying to make is:

Mana efficiency =/= Mana regen and it should be used to say that x.x SP = x.x Mp5

When optimizing your gear you don't choose a piece because you will save other people mana.. While it may benefit the raid as a whole that you can cast more spells or have them be more effective, that isn't the goal of this discussion and should be an obvious fact. The concept I am trying to point out is that when comparing stats it is not so simple a comparison and really you shouldn't try to compare regen stats and throughput stats.

Really each stat should be looked at for its relative value in throughput and regen. You should then gear such that you reach the desired levels of throughput and regen to match your playstyle, composition, etc.

Generally speaking increasing throughput -> increased efficiency -> reduced regen required and hence you can fulfill your role at a lower level of regen (possibly). While that relationship is good to know it is not necessarily true that having better throughput means you require less regen. In all likelihood situations will arise where the additional throughput is used at length and completely negates any mana efficiency that provided the opportunity to run with less regen and you will be in the situation of looking for Innervates and running OOM. I am merely trying to show that efficiency does not create regen it creates the potential to require less regen for the same amount of healing.

#1
It is in my opinion perfectly acceptable when evaluating the throughput provided by haste, to treat it as you have. It does not provide the opportunity to say that haste in any way impacts mana regen or mana efficiency... Unless you tie it to a change of spell that creates an increased efficiency such a as a transition from FH -> GH.

Possibly you mistook my point on HpM to be about haste.

The statement:
"So until you can fully quantify that you will cast X-1 casts vs. X casts you have netted no actual mana consumption gain. Furthermore even at the point that you have reached a consumption gain you have not improved regen you have only reduced the regen requirement of the encounter."

Is not Haste related it is HpM related. So to go into further detail lets say that your FH HpM is 11.15 for 5812 average healing. You are in a situation that requires casting two FH in period of time and is well within current bounds. Obtaining some gear you improve the FH HpM to 11.56 for 6027 on average. In this scenario does the improved efficiency provide you any gain? Does it reduce the regen requirement?

- Only if you required the second FH for 215 HP would it be a gain for 2 cast scenario.
- It requires 26.78 casts before the more efficient version nets a reduction of mana required equivalent to 1 FH over the duration of the fight. Given that all heals are 100% effective.

What further complicates this discussion is that HpM gains create the potential for "extra" casts similar haste. The mana efficiency can provide the opportunity to get the same healing on targets for less casts creating the space for either an additional cast (on another target) or the ability to refrain from casting and conserving that mana. This choice leads me to the belief that you shouldn't use these types of relationships to create any hard/fixed relationships between the throughput and regen stats.

Regen / Throughput Stat Weighting
In the Discipline thread I did provide a "combined" stat weighting which when I edit the main post will be removed because it creates trouble and is inaccurate depending on play-style and assignment.

The problem with combined weights is the basis: What drives the SP:MP5 ratios of (0.6:1) and (2:1)?

Once you progress from that point the entirety of gear, gem, and enchant selection really falls back to the assumption. That assumption can not be firmly rooted in any clear mathematical model for "general" healing. Because in essence you have said that the throughput requirement is now twice what the regen requirement while it was only 60 percent previously. Quite a significant shift.

For the masses I can agree that some combined ( x.x SP = x.x Mp5 = x.x Haste = x.x Crit = x.x Spirit = x.x Int) makes life simple. It really isn't the appropriate approach for every situation and I choose to not use it when gearing for myself.

For Discipline healing I find that most fights my healing falls into a rhythm of casting. That rhythm can be quantified into a number of casts per period of time, which can be extrapolated into an amount of mana required per time and per fight. This can yield a mana requirement and identify whether you are above or below the desired level and drive your gearing of regen stats. From this personalized information you can also account for the "I would have casted more but I know I would have gone OOM" and then add to the mana requirement to support what would have been optimal for you. After I reach the point of regen desired I stack throughput stats as completely as possible.

The resource (mana) is my primary concern because without it nothing is possible.

"The real value of haste is what we can call the cascade save. This is where the small increments you save on each cast add up over 2-3 casts to being able to put out another heal on yet another different player who would otherwise have died."
This cascade is also completely broken every time the raid damage dips into a lul again, as it tends to do on almost all hard modes. You have a fairly short period of high healing output, and then a slower period, meaning you only feel the haste if it allows more casts within the very short maximum HPS situation, oftentimes periods of just a 5-10 seconds.

Calculating how many more spells haste would allow you to cast over a complete encounter is, as so many haste proponents liked to point out earlier, completely irrelevant as it doesn't change the total HPS of the encounter, therefore you're not going to cast as many heals as that.

So the trade-off becomes how much clutch HPS you can put out if you put X amount of itemization points into Haste as opposed to Crit or SP, and what this is going to cost you a) during the max HPS periods and b) in lowered healing output when healing is slower.

Haste Saves Lives Fallacy

I just realized this is not actually true. It's a pretty obvious equation, someones taken damage and needs to be healed up quick, so haste is going to save his life, naturally. But what do you throw at someone who's just taken damage and needs a quick heal? Instants. PW:Shield, SoL proc Flash, Renew...or in an extreme case, a short cast time spell like Flash, in which case each point of Haste does less than it would for a long casttime spell. But that probably didn't heal him full, so you might figure haste comes in as how fast you can heal him to full. Well, no, not unless you're the only healer, otherwise by the time your 2nd heal lands, there's prolly a reju ticking on him and a FoL or shock from a paladin and probably a LHW from a shaman. So what did haste do for you? Well, incase you were casting right prior to this, it might reduce the cast time of your current spell(if you chose to finish it as opposed to canceling), or it might shorten your GCD. So for Haste to save an individual targets life, it needs to be a window of only fractions of a second. And you pretty much get a bigger benefit from just improving your reflexes in general.

Proposition for Stat Weight System

Seeing as there's been quite a bit of discussion about Max HPS, I figure it might be worth calcing Sp vs. Crit. vs. Haste in a Max HPS situation. This would entail calculating per point increases in Max HPS over periods of 5, 10, 15, 20, 25 and 30 seconds. I suppose you can extend it further, and indeed FF p2 is an argument for 1-2min Max HPS calculations, but for a "general" view the 30seconds should be enough, and should not distort the calculations too much in favor of Sustained Max HPS.

This data could be group in terms of showing best practice gearing for short(5-10) second intervals, medium(15-20) or long(25-30), as well as a General Max HPS Weight for the whole range.

Obviously this will differ to some extent based on gear profiles, but for the assumptions of these calculations you might be able to ignore Haste/Crit default values and instead simply have a default SP value for X tier of gear, which is easy enough to figure out since it's based on iLVL.

In the example I provided the difference provided by enough haste to knock .3 seconds off a flash heal / instant cast means that in the time to do 4 casts you can now do 5. This is an 6 second block of time which is very relevant in your burst healing scenario. Being able to put out an entire extra cast on the target of your choice is insanely powerful when it comes to actually saving lives. All it takes is 16.66% haste to allow you to fit a 7th heal into the space you had 6. (A 9 second window). This translates to 11% unbuffed which is trivial to get to.

Haste allows a fine tuning of how and where you heal. In a good raid players die because the burst healing ability of the healers is less than that required by the encounter and there is damage spread all over the place require OH CRAP healing triage. Haste increasing the number of targets you can service is the most powerful thing you can ever do in these situations, 9 times out of 10 the total size of the heal is fairly irrelevant provided it is in the 3-5k range. Usually it's a case of get any heal and live vs get no heal and die. Haste greatly increases the chance of getting the heal off so is by far the most valuable stat to stack for burst healing situations. Unless your tank healing a runaway freight train you don't generally need to worry to much about the size of an individual heal as any heal will contribute to a save.

Your comments about the redundancy of flash healing a target a second time has nothing to do with haste and is a function of the healing team working well together and having a clear understanding of their responsibilities in the fight. What did haste do for me? Well he isn't full but he's out of the danger zone so I'm actually doing triage on someone else who will die if not attended to immediately. Haste doesn't directly save lives when healing a single target if you are directly trading off with power, what it does is allow you to save extra targets in a small space of time. It also allows your healing on that single target to be spaced more closely, it's why hots that tick every second are so much more valuable than a hot that ticks every 3 seconds despite having the same overall healing potential. Smoothing damage and healing is always valuable and this is what haste does.

What you are basically saying is: people never die because there's always some healer available who has a heal in the pipe. Quite obviously, that's not true, otherwise people wouldn't die, right?

As for instants: PW:S is nice, unfortunately the targets must not have a weakened soul debuff. Renew? No, sorry. The instant part of it (for holy) is too small. You don't try to save someone with 2k. Perhaps if you are running and have no SoL proc in the pipe.

You can argue that it's very difficult to quantify the live-saving effect of haste (healing granularity discussion incoming), but you cannot deny the effect.

The best "life-saving spell" that a priest has in my humble opinion is Guardian Spirit and paired with the glyph that resets its CD to 1 min if not used, it can be a real benefit. Plus it increases the healing that target receives by 40% while the Guardian Spirit is watching over the target. So if the target does not die, it receives healing by 40% more and if it does die, the Guardian Spirit sacrifices and restores the target to 50% health. That is a real life-saving spell.

I'm scaling a lot of int atm and I've noticed that when I play disc my PWS cost 666 mana and it gives me 712 mana because of really huge manapool size. So i have almost unlimited mana.

"When optimizing your gear you don't choose a piece because you will save other people mana.. While it may benefit the raid as a whole that you can cast more spells or have them be more effective, that isn't the goal of this discussion and should be an obvious fact. The concept I am trying to point out is that when comparing stats it is not so simple a comparison and really you shouldn't try to compare regen stats and throughput stats."

Absolutely disagree; anything that contributes to the raid is a worthwhile goal (the only goal that matters really). Also the comment that I was talking about was you discussing throughput and efficiency, not regen. I agree that regen and throughput are separate topics and ought not be directly compared. Efficiency and throughput are not. You cannot raise efficiency without also raising throughput. The question comes down to degree. If you chose to ignore the regen component of efficiency stats, that's fine, but throughput and efficiency are linked topics. Haste is the only pure throughput stat, every other throughput stat also increases efficiency.

Gear upgrading in general benefits the raid group.. If it was a discussion of optimal raid gearing I would agree. Then you would get into the discussion of the worst geared player or the worst in-slot item is the one that receives upgrades. My thought is this is a discussion of the relationship of stats and how it effects your individual ability to contribute.

Efficiency and throughput are linked... I am a little confused at the goal of pointing it out. If you are trying to argue that there is a definitive regen component I would like to see how you would define that.... Because as I see it all you create is the potential to A) possibly reduce the mana requirement of a fight and hence reduce the necessary regen required to do the same total healing that previously required more mana or B) that the efficiency is converted into additional casts and as such the mana requirement does not change and hence the regen requirement remains the same and all that happens is a pure increase in throughput over the course of the fight.

In the (A) case then mana efficiency does correlate to a regen savings and could be quantified as a Mp5 value and in the (B) case the mana efficiency is a virtual placeholder that really converts into additional throughput and can not be quantified as a Mp5 value. Because you can not quantify which of the two available options is used on a regular basis for the general population, you can not use them to correlate SP to Mp5 in general.

I have been pondering this for some time. Personally, I no longer think this is a bug. Blizzard has actively disabled this for the Vezax hard encounter. I haven't seen any occurency of multiple mana returns on that fight in the combat logs. So, since they do have the code in the game to disable this behaviour, it must be intentionally active on the remaining fights.

Maybe this was done make discpline priests viable on encounters with massive raid damage like Freya+3.

Perhaps you're not considering this in the right context. You seem to be examining haste in a situation where all the healers in your raid are available to cast on the poor soul (presuming it's not a tank) who's taken damage. We can find a much better example of how haste saves lives in something like hard-mode Mimiron. There is a ton of raid damage in that encounter, and it's an extremely mobile fight. It's very likely you have at least one and probably more than one healer who's either out of range, moving to avoid fire/rocket strike/bomb bot/etc., or is healing a tank/OT who's taking damage. Either way, they can't stop to throw a holy shock/LHW/Rejuv on the person who's taken an unlucky hit and whom you're trying to save.

Even if you haven't been stacking haste in your gear, it's easy to see here how haste can save that player without instants coming into play. Having done this fight as both holy and disc, there are several ways you can react to this situation. If you're holy on this fight, you're likely stacking up Serendipity (provided you specced into it, of course). If you're disc, you've probably got penance up, and failing that, you have PW:S and a hasted imp. flash (provided you specced into Borrowed Time/Imp Flash Heal) to buy you and your fellow healers some time to get a more solid heal on them. In that situation as holy, I can slam a 10k minimum heal on that player in 1.4 seconds. As disc, same deal using penance. The PW:S/flash is going to take a little longer just by virtue of the GCD involved there, but the PW:S is going to prop them up for the time it takes to wait out the GCD and hit them with flash/penance even if we're in phase 2 with Rapid Burst and Heat Wave ticking on them. That healing haste is going to mean that we get that person healed up fast enough to start on the next person who's taking damage (and there will be a next person). These haste talents absolutely save lives, and combined with haste gear and an encounter involving heavy raid damage and/or movement, it's easy to see the effect.

The case I put forward was one of a single person needing a quick reaction heal. When it comes to heavy raid damage encounters, I don't see how haste does anything at all tbh. If we take your example of FF(I assume you're talking p2 or p4), then everyone is taking damage, and casting single target heals just keeps you going from one crisis to another. What you need to be doing is finding spots to cast PoH, casting coh/pom while moving, and if you specifically end up in the situation you describe(most often only because you weren't getting enough overall raidhealing out there), you use a instant flash or pw:shield. As disc I'd apply the same reasoning, you need to spec into larger poh raidius and use shield/penance to get that spotheal off.

Now you might argue that haste lets you get off more poh's, thus being valuable for this fight anyway, and in some fights of this type that might be true, although in those cases we get back into the discussion of haste being a mana-inefficient way of doing this. However, if we consider FF specifically, haste again is only worth something if it enables you to get off a cast when otherwise you could not, or get off an additional cast. However, again better positioning will buy you the time you need, whilst crit gives you high throughput which is extremely unlikely to be wasted whilst also not costing you extra mana.

So as far as I'm concerned the question still stands if haste delivers enough increase in max HPS over crit to justify stacking it, because the other benefits of it are negligible.

I always used to be a huge fan of holy raiding and haste over all. It really was worth it quite a while.
The problem is that we don't seem to have an alternative for haste/sp when it comes to throughput and no matter how much haste or spellpower you gain, you will not be able to compete with a good resto druid spamming Rejunivation over and over.

Anybody else worried about that? I always felt like a good raid healer, but when I take a look at a druid healing a raid with 70-80% overheal and having no mana issues at all ( World of Logs - Real Time Raid Analysis ), I just become desolate. Of course a holy priest will always fill out a viable role in a raid, but it just sucks being behind like that sometimes. I hope that they will either nerf droods or buff us a little bit, altough I feel this is not really necessary anyhow. At least there is Discipline..cough

You're looking at this from the wrong perspective. Druids compliment the healing team, let their Rejuvenations top off the raid; but in order for them to do that, they need people like Priests to quickly re-act to burst damage and to bring people back up while they spam-away at their Rejuvenation.

Don't get me wrong, Resto Druids have amazing tools, and they can react to burst as well, especially with Swiftmend, Regrowth and Nourish. But they can't spam the raid with Rejuvenation and Nourish/Regrowth at the sametime either.

Healing meters are bad. It doesn't matter who is #1 and who is #6 (although if your Disc Priest is #1, something might be wrong).

Just remember, you enable the Druid to spam those Rejuvenations. Healing by it's very nature is support, we aren't the superstars. To steal a quote from Amera/Sky, Healers are like the Offensive Line, we allow the Tom Brady and Peyton Manning's to look and act like the super-stars they are, but when Brady and Manning get sacked or fall down, the Offensive Line gets the blame.

It's largely a fuction of encounter design.

Rejuvenation is possibly a little overpowered (the mana cost in particular is insane), but the more important factor is that Blizzard is absolutely dead-set on pushing massive constant raid-wide AOE damage into their fights. The weakness of HoTs has always been overhealing; HoTs on someone who isn't taking damage are worthless. Remove that weakness by making everyone in the raid take constant damage, and it's not so surpising to see Resto Druids dominating on raid healing.

If you look at encounters where damage is much more spiky and random (Jarraxus is a great example), you see Resto Druids performing quite poorly on raid heals.

Yes you are correct. The SP:MP5 ratio really is the critical assumption. What ratio of SP:MP5 you use is really the same as deciding what percentage of throughput vs regen you want from your stat weighting. It is the method for equating healing equivilence points (HEP - throughput) with man equivilence poins (MEP - regen).

0.6 was taken directly from DwarfPriest.com, who alluded to having a basis for this, although I could never find the source. MK (author of DwarfPriest) of course stopped blogging so I never found the source. I was fairly new to this theorycrafting when I did my 3.0.8/3.1 stat weights so I just took took MK's ratio as presented. It worked very well for T7 and less well for T8.

Shortly after the 3.1 stat weights I discovered from my own experience in Ulduar that mana and mana regen was no longer an issue. It never ran out. So when I started working on the 3.2 stat weights I resolved to increase the ratio from 0.6:1. I think you (The Doctor) were using 1.5:1 and I started with that number. It didn't really seem to go far enough in terms of bias towards throughput so I settled on 2:1.

So the short answer is that the ratio is really personal preference. I choose and published using 2:1 because that felt right to me and I know there are thousands of readers out there who don't care to read forums like EJ and make that decision themselves.

At the end of the days, due to the relative limited options for sourcing top-end gear from, as long as you go for the highest ilvl gear you can, you are pretty much upgrading. The details are more for arguing over BIS and that sort of thing. The only real exception to this is trinkets where there are very clear mana regen and through put options and where sometimes an ilvl 200 item is better than an ilvl 232.

After all this discussion on Haste and stat ratings... It really started me thinking. I have been of the mindset that throughput and regen need to be measured in their own rights, and for a static score system I still believe that to be the case.

If you use a spreadsheet or some other means where the scoring can be dynamically calculated based on the current gear and by an outlined cast composition and time of encounter... Then you can come up with an accurate current weight. You can download my spreadsheet to see what I am talking about. It currently handles primarily Disc Priests.

So in updating this spreadsheet I was working toward a common single comparison system and used the acronym SHC for Sum Healing Capability. What I came up with is that all stats are throughput stats in some way shape or form.

SP/Haste/Crit
Fairly obvious that they are throughput stats and the means by which they provide the gains.

Spi/Mp5/Int
Not so obvious but here is the reasoning. If you operate with the base mana pool what is your capability to heal? Very limited no matter how much SP/Haste/Crit you stack. Through strict regen stats and through the additional mana pool of Int we increase our ability to produce healing and hence throughput. It is quite obvious that if we have mana we can cast and if we do not we can not. It is critical when converting these stats into a throughput equivalent that we understand the mana required, encounter length, and spell composition as these determine what the ideal level of mana regen to support that throughput would be. Anything above the regen required does not contribute to additional throughput, so in terms of throughput regen stats are soft-capped.

In example, Billy Joe the priest is healing an encounter and would like to cast a FH every 2 seconds (super simplified example). The encounter requires that this level of healing be maintained for 60 seconds. What is the regen required to support the throughput of FH at this rate?

FH costs 591 mana casting one every two seconds is 295.5 mana per second and correlates to a balancing point of 1477.5 Mp5. This is widely variable based on mana pool size, so evaluating at varying int / mana pool sizes we find that....
924 Int -> 17443 Mana -> Requires 0 Mp5 to support this level of throughput for 60 seconds and end OOM.
700 Int -> 14083 Mana -> Requires 303.91 Mp5 to support this level of throughput for 60seconds and end OOM.


Summary
Given a specific encounter you can determine the appropriate mana cost to support the spell composition and throughput required to fulfill your role in the healing lineup. Based on that mana cost and the regen stats you currently have, further regen stats may or may not have value. At any point you can say "I would have" casted more spells or more expensive spells given that my mana could support it, you are in a position where your regen may not be high enough.

From a mathematical evaluation of the stats Mp5/Int are the highest throughput stats for Disc priests until you reach the point that mana regen is no longer required at an additional level. The basic comparison would be Mp5>Int>SP>Haste>Crit=Spi, or very close there about... This is very dynamic so don't take that as the law or a static approach.

For Playing with my spreadsheet to look at the results, it is important to set the % on the 'Healing' tab as the composition of spells cast over the course of the fight based on your playstyle. If they sum to 100% then you are assuming chain casting the entire period of the encounter length set on the 'Talents & Misc' tab. Modifying those values changes the 'Mix Mana Cost' on the 'Healing' tab and impacts the 'Longevity' line that is visible on several tabs. I have it configured such that once the longevity is greater than or equal to 100% then regen stats do not contribute to SHC weights as you have reached the point of excess regen and should only be stacking the other throughput stats. One important note is that on the version currently uploaded Penance is assumed to be casted on CD.

Many of the trinkets are not fully working so it may be difficult to play with just the trinket comparisons at this time. I hope to improve that soon. The Spirit portion of Spark of Hope is working but the mana reduction portion is not. If anyone finds problems in the spreadsheet please let me know so I can update it, it is very much a work in-progress.

Trinkets and Consumables(Food, Elixir/Flasks, and Glyphs) are definitely the quickest and easiest way to change your focus.

I think this argument really comes down to thinking small differences are no difference at all. If someone takes an aweful lot of damage and is about to die and needs a heal, there is a good chance that I am already on a GCD, since I nearly always am. There is another healer or two that can do something about it once their GCD ends. They might have a HoT on them that will buy time if it ticks. So assuming someone needs a heal in the next .5 seconds and we have three healers on GCDs who can save them and a HoT that can save them that ticks every three seconds, and we have no particular reason to think that any of those healers is at any particular point along their GCD the chance they live is 1 - (1 - 1/6) <for the HoT> * (1 - .5/healer #1's GCD) * (1 - .5/healer #2's GCD) * (1 - .5/healer #3's GCD). If we all have about 25% haste then they will have about an 83.45% chance of living. If one of those healers increases their haste by 1% that means the person now has an 83.55% chance of living.

That's a pretty meagre increase given the narrow-ness of the situation, and of course if there are more healers with abilities that aren't on cooldown, or there are more HoTs that tick for enough the difference that 1% haste makes matters less. But since you are sharing healing duties and there are HoTs ticking and Judgement of Light Proccing, etc., how much difference does any other stat make? Would that 38 spell power you could have had instead saved a life in a similar borderline situation where a person is about to die? Would 33 int have prevented you from running out of mana? You may say that changing your flash heal from 1.19 seconds to 1.18 doesn't make a difference because what are the odds that *that* is exactly how much shorter it needed to be. But what are the odds that the 40 extra healing you could have had on it instead are precisely the 40 healing the person needed? Remember that spell power has the same problem you describe for haste. If three other healers all drop a heal at the same time, more spell power is probably just more overheal; but we all know more spell power is better.

Small differences are small, but they matter. They all matter. The question is not which stat doesn't matter, it's how much each stat matters relative to one another.

See my armory page, I have been testing int stacking, and it has been competitive thus far in current Ulduar/ToC content.

Been enjoying reading the discussion here on the relative value of Haste and its changing value in relationship to other stats as those stats increase. I think the top things I take from it all is that the values of our different stats in fact change relative to one another as our gear improves, and that at differing gear progression levels, what should be considered our most important stats to focus on changes.

I would have to brush up on some of my old college math and possibly even learn a bit more to really get into the math discussions, but I can understand the arguments and generally the math sufficiently to take what has been said here and pair it with my own extensive experience as a very active raiding holy priest in the game to arrive at some simplified conclusions I will try to set forth:

Early on as a holy priest in raiding, I think it is most important you work on your mana regen, because unless you have that fuel in sufficient quantity, it matters not how powerful the other stats are for the most part, since without sufficient fuel, your spells do not get cast, and those stats are mostly benched. Thus at the early levels mana and regen seem to have the highest relative value.

Once you get sufficient mana and regen that you can cast at least as much as needed through the end of the encounters you are attempting, past that point mana and regen are relatively useless in additional quantities. Then it makes sense that you would turn your focus to other stats.

I feel that SP is the next stat to focus on because it makes all my spells get a bigger bang for the mana cost, and thus improves my throughput the most, while at the same time in effect further increasing the mileage I get for the same mana. At this point Haste would have more relative value than additional mana and mana regen, but less relatively than SP.

But there seems to come a point at which additional SP translates into less effective healing in actual game conditions and more overhealing, and at some point that in effect diminishes the value of SP relative to Haste.

So now I am at the point I have all the mana and regen I need to play full out to the end of the encounters, and I have so much SP that the effective healing I am getting from adding more is diminishing, and it is at that point where if I add additional Haste, I get the biggest and best return for adding it, relative to adding additional other stats.

Now how to quantify those tipping points for mana and mana regen, and then for SP, is beyond my current math skills without some real refresher math study and perhaps further math learning, but that is not really necessary I think for my point in this post, which is to set out in fairly simple terms some general guidance for developing holy priests, which is as I have stated:

1. First get your mana and regen to that tipping point....THEN
2. Get your SP to the next tipping point.....THEN
3. Go for Haste.

Hope this contributes to the excellent discussion already here, if only making it easier to understand these general principles, and to expose them to constructive critique.

I can definitely buy the gearing strategy :
1. First, go for regen.
2. When you don't need more mana, go for throughput.

But I find it difficult to say that for throughput, you need to focus first on spellpower, then on haste.
You basically need both at the same time. Relative weights might shift, but there is no clear turning point.

Throughput is increased mostly by spellpower and haste. The interest of spellpower (resp. haste) grows as your haste (resp. spellpower) grows.
More than that, you're throughput is roughly affine in both stats. It might be the case that at very low level of gear, one stat is clearly superior to the other, but after some values, the optimum will always be to keep some ratio between spellpower and haste (or, in other words, to increase your haste rating by x when you increases you increases your spellpower by 1, with x >0 ).

Now, the only way to change this is to use granularity argument (ie. to say that there is a specific value where the interest of one stat decreases dramatically). That's what you do when you're saying that there is "a point at which additional SP translates into less effective healing in actual game conditions and more overhealing". That could be meaningfull for one precise fight, with one precise healing team and assignment set. However, the damage pattern is not the same for different boss fights, and the healing requirement is not equivalent. You don't need to heal your target for the same amount on, let's say, Razorscale, XT or Mimiron. You also don't have the same time before your heal is needed.

If you want to gear for a very specific encounter, then you can say that spellpower is to focus on till you reach a certain threshold, because at that threshold, your flashheal (or whatever spell) is going to heal for X HP, which correspond to the boss ability. But that's not true for all fights.

There is a clear threshold : you don't want to heal for more than the player total HP, and a 15k flashheal would overheal in lots of situation. However, we're nowhere close to the situation where our "small" heals are close to "too big". I don't see any reason not to maximize throughput at all time.

I've noticed that many priests are stacking int and haste for both specs.

I'm actually stacking sp and crit (sitting at 30% unbuffed as Holy).

Am I doing it wrong?