Big mistake. Damage absorption is not healing. 1) No overheal, 2) damage is never applied. The fact that healing comes after the damage is applied makes all the difference in the world, because if the tank drops below zero you cant heal that back up. We all know this is why inspiration is powerfull. Healing damage instead of absorbing it produces larger variations in tank health than absorbing damage in any way by default. Just how things go.

Removing 20% of aegis efficiency is obscenely wrong. The likelihood of you getting back to back crits without the tank getting hit even with 25% crit rate and 50% dodge/parry is something like 3%.

The tank having mitigation does not mean the value of healing or absorbing damage increases. It does not. What matters is how the damage filtering through the mitigation is dealt with. 900 healing is not 900 healing multiplied by what is absorbed by mitigation its 900 healing. However its actually no healing at all. You forgot overheal With 30-40% overheal the extra healing power from holy is reduced in value greatly but PWS and divine aegis are not. On top of that you also forgot improved inner fire which probably stacks with enlightenment and twin faiths. That further reduces the difference between holy priests and disc priests and the fact that grace increases healing from other sources.

Also inspiration always counts. It does not matter whether other healers can add it. What matters is that the tank healer can keep it 90% of the time without help.

The damage absorbed matters only after mitigation. You cannot consider the effectiveness after damage mitigation from the tank works its magic. That happens whether you are there or not. What matters is how you affect the actual damage taken.

Lets say the tank is taking 2.5k DPS after inspiration. Add to that grace for 6% less and you get 2350. Add a 2.5k shield from aegis every 12.5 seconds --> -200 DPS. Add a 3k shield every 15 seconds --> -200 DPS. Total of 1950 DPS on the tank. 1950/2500 = 78%. Tank damage reduced by 22%.

What disc priests bring to RST healing that holy priests don't is an instant 1sec 3k absorb which actually returns mana to him and pain suppression in case shit hits the fan. That is not to say that disc priests are gods at healing RST and holy priests are bad. Holy priests would certainly be very powerful.

Having a healer spec ImpDS/Holy would be a terrible waste. Without the full complement of deep holy talents a priest is a true gimp spec, while deep disc is not gimped at all. The same is true with grace/holy build. Also you dont really want more than one disc priest in the raid.

Full disc is equivalent to full holy on tank healing and healing RST abilities. Although holy has much less damage reduction it has more HPS, more heals per second and can smooth out spikes nearly as well as disc can and in some situations better by being capable of maintaining massive overheal. One healer will certainly be specing disc for a few select encounters but otherwise disc would be non-essential but still fully raid viable. Mixed spec wont be. Its not possible to even get mental agility now, without being gimped. Not getting 2+ ranks of divine providence and not maxing, test of faith, serendipity and IHC is now a huge loss. Even lightwell and healing prayers are probably very hard to skip now.

I envision disc with a different healing sequence than what priests are used to. Also a large part of it is not immediately visible, since it involves damage that never happens. You need a controlled experiment to fully gouge its value and have every talent working. It will probably take some time before ppl figure that out. Until then they are bound to try gimp half baked specs which are just as bad as the 20/40 spec for holy priests (no CoH, no impDS) is now.

Greater Heal (Rank 9) heals for 3950 to 4590 (4270 average).

Discipline Priests get Twin Disciplines (5%) and Enlightenment (5%), so they'll heal 4708 average in 2.5s (Divine Fury). This is 1883 hps.

Holy Priests get Twin Disciplines (5%), and Spiritual Healing (10%), so they'll heal 4932 average in 2.5s (Divine Fury). This is 1973 hps.

Holy Priests then also get Improved Holy Concentration. The chance that at least one of the three previous Flash/Greater Heals have proc'd clearcasting is 40.7% meaning you have the equivalent of 60% * 40.7% = 24.4% haste over time, giving you 2454 hps.

Holy Priests are almost certain to get more bonus spellpower from Spiritual Guidance than Discipline Priests get from Improved Inner Fire.

With equal gear, Disc and Holy will have equal critical. Divine Aegis provides a buff of ((critical rate * 0.95) + 1) compared to the normal advantage of ((critical rate * 0.5) + 1):
10% critical: 9.5% vs. 7.5% (2062 hps vs. 2638 hps)
20% critical: 19% vs. 10% (2241 hps vs. 2699 hps)
30% critical: 28.5% vs. 15% (2420 hps vs. 2822 hps)

We'll disregard Test of Faith since it's difficult to model and just emphasizes the Holy advantage.

In terms of scaling, we'll assume that current coefficients double. That gives Discipline Greater Heal a (3 / 3.5) * 1.05 * 1.05 * 2 = 189% coefficient, while Holy Greater Heal gets ((3 / 3.5 ) + 0.2) * 1.05 * 1.1 * 1.24 * 2 = 244% coefficient. In terms of coefficient/second, Discipline has 75.6%/sec while Holy has 121.0%/sec.
It should be noted that under virtually any interpretation of spellpower changes, spell critical is a waste for either healer since spell haste outperforms it in all respects except for mana consumption at any level of +spellpower. But we'll assume that there's some actual reason to take spell critical. Under the 30% spell critical assumption, the coefficient/sec disparity shrinks to 97% vs. 139%.

So if we've got 2000 spellpower @ 30% critical, our Discipline Priest is mustering 4320 hps. Our Holy Priest with the same stats is mustering 5602 hps - a 30% advantage in throughput disregarding Test of Faith.

Since Grace confers a total benefit of around 12.4% to the tank, it should be obvious that a single Holy Priest will outperform a single Discipline Priest in single target throughput. What's less obvious is that to make up this gap in performance, you need about 11k hps directed on your tank. With a healing crew of 4-5 (as indicated by the developers), this means that over half your healers are doing nothing but spamming high throughput heals on the tank.

I'm just not seeing much change in role for Discipline Priests in WotLK. Grace will help them heal 5-mans, but it will be almost worthless in 10-mans I imagine. In 25-mans, it's more of a coin toss but it definitely seems like the coin is landing on "don't bring a Discipline Priest". In PvP, the improvements to PW:S will make Discipline Priests incredibly tough to defeat, though.

This was a request that a few people made in alpha, but it's not really under consideration according to blizz. Best we can hope for is that they make poh centered around the priest but not limited to group. No word on if they actually intend to implement any change though.

The improve PW:S should reflect damage back to the boss. I would assume it is minor but during a 5-8 minute fight how much improved raid dps do you get from throwing imp PW:S around (assuming you are using it as a primary source of healing prevention)?

Strange approach you have to the new talent trees. This is the second time you defend lots of mediocre talents and poor scaling because we get a buff at the bottom of the tree (seriously, your attack on me needing to top meters is not even funny, please just stop for your own sake). Yes, Grace is good, but it doesn't mean that we should be happy about terrible scaling. Just look at other healing trees and you know what I mean (or read Kortar's post, numbers look good to me).

They need to revamp disc further to make it a good spec for PvE or it will stay as an excellent PvP tree. Less points wasted on boosting +healing and more abilities/synergies would be a good start.

Sorry to derail, but could you clarify this statement please?

The idea is that if you extrapolate from a normal 5 man group of 1 tank, 1 healer, 3 dps into 25 man content, you get 5 tanks, 5 healers, 15 dps. Right now you usually have 3-4 tanks and 7-8 healers though.

OK, look ...

Do you really want to be a one-trick healer? Someone who is only brought to a raid because of your ability to keep a buff up on a tank? The first healer to sit when a fight is on farm, or when the boss doesn't really hit hard?

If you're doing a fight in Naxx v2.0 where the tank is only taking moderate damage, and most of the damage is AE, do you really think there is a place for a Discipline priest? That's what we're asking. And most of us are concluding no.

As much as some people are trying to make Grace out to be the be-all and end-all ... the new Affliction tree for warlocks is quite strong. I would not be surprised if a warlock with a phase-shifted imp because standard in WotLK raids. They bring 5% reduction to the table. Why would you bring a gimp healer (and yes, the healing is gimp, stop assuming we're too dumb to see that it is) to a raid to provide an extra *1%* reduction in damage and +6% healing, when you could just bring a healer who does 25% more healing on a single target? The 6% only scales to beat the 20-25-30% when there's a lot of healers taking advantage of the buff.

I'd love nothing more than for Discipline to be raid-viable. But crit absorption shields and improved PW:S and Grace are all the same pony -- extremely hard-hitting bosses that swing slow. You get Grace up, and reduce all hits by 6%. You put a PW:S up before each spike, to lessen the nastiness. And you get crits, which increase your personal healing and reduce incoming damage again.

On any fight that isn't (basically) Patchwerk v1.0 or Brutallus, there just isn't enough incoming damage to justify it. You pay a very hefty price to pickup Grace and Divine Aegis, not to mention Borrowed Time. Most of us are looking at the talents, looking at the flexibility you lose, and putting Discipline in the role of "I'll respec if I have to for a hard-hitting boss, otherwise, deep Holy ftw".

Well that is the glaring flaw with my scenario, and I tried to admit as much by saying the Disc priest is going to bring strictly worse overall healing and much, much, less flexibility (not in that post, but previously). Alot of this discussion is pure speculation since we have no idea what the encounters will be like, but to be clear I agree: If you don't need Grace, then Discipline is worthless.

Strange how a reduction of 3% can swing a tree so wildly from good to bad, isn't it? When Grace stacked up to 9%, there seemed to be much more of a consensus that the first priest in any given raid would be Disc, but when it drops to 6%, Holy becomes much more comparatively appealing (and note that I agree with the swing back to Holy). Nidaba's emphasis on the loss of flexibility in switching from Holy to Disc is notable, but if Grace were restored to the 9% damage reduction, would it become viable again? Are 3 percentage points really that vital, or has perception changed on the concept of Grace as a whole?

At 9% in scenario 1 that I posted, the disc priest would actually give more total hp/s and 9% damage reduction.

In scenario 2, the disc priest would give slightly less total hp/s, but when you factor in the 9% reduction it is still strictly better. So yes, that 3% (to each end of the buff) makes quite a difference.