When considering the efficiency of GHeal it's important to include Train of Thought. By casting GHeal instead of Heal you can use Inner Focus every 6 casts instead of every 18 (approximately, depending on your haste), that bonus pretty much erases any difference in HPM between the two. As long as my target isn't going to get overhealed I'll always use GHeal over Heal.

It isn't so much that haste is irrelevant, as that your proposed solution of replacing GHeal is inaccurate.

Now that PW:S spam and the BT haste 'soft cap' are no longer present to the same degree haste can be useful. Though in a mana constrained environment where efficiency is the most important factor... Stacking haste isn't very reasonable as a primary objective. If at some point we need to cast maybe more PoH in an interval of time then we will have more reason to give haste a higher value.

As Carnathagia pointed out Crit is better than Haste... Though that doesn't mean get no Haste only that you shouldn't be stacking it at cost to a more valuable stat.

I didn't say no haste, I said lowest priority, other than say hit/stam/etc. of course. Basically what I'm getting out of this is, if you're missing any of the other stats on a piece, you should reforge it from haste. If there is any minimum value where that doesn't hold or somebody disagrees, please share. Maybe you'd have to use specific gear combinations to be sure, but it doesn't even sound like that's a factor.

Alright, so now I'm curious, since it seems there's two possibilities on how to heal my tank.

On the one hand, it's recommended by the OP to use a SoS-based healing rotation, using Heal to reduce the duration of Weakened Soul, and thus get more shields on my tank.

On the other hand, it seems like it's being suggested to use Greater Heal in place of Heal, and thus get more uses of Inner Focus (meaning more 'free' heals).

Is there one method that's far superior to the other, or are there certain situations where one style is better, and certain other situations where the other is better?

I'm still new to the healing scene; I'm used to being a dps, where everything's black and white and there's always a definitive 'best thing', so I'm trying to get a lot of insight from experienced players etc.

With Train of Thought, GHeal's mana efficiency is roughly identical to Heal's.

Using the figures and gear set from the OP: Heal has a HPM of 6.67, while GHeal is 5.93. Train of Thought reduces Inner Focus by 5 seconds, which is roughly equivalent to a mana cost reduction on GHeal of 5/45. 5.93 / (1-(5/45)) = 6.67 HPM including Train of Thought. In practice the figure will be slightly lower since Inner Focus will be sitting unused a few seconds here and there, but in general we can state that both spells have roughly identical HPM.

This implies you should GHeal if it won't overheal, otherwise Heal.

With Strength of Soul (healing a single tank) you want to fit at least one Heal into each 12 second rotation to take advantage of Rapture asap after the ICD expires.

Actually, with Shield currently being less efficient than both Heal and GHeal, I believe tank healing disc priests should configure their UI to show Rapture ICD, and only shield the tank when the ICD is up. This makes more than one point in Strength of Soul pointless.

That's a valid point, and if you follow that line of thinking through, then we're currently only shielding the tank for more throughput* during tank-pounding phases (in which case we won't be using Heal in our single target rotation anyways), or for keeping up the Weakened Soul debuff.

But if that's the case, then the points in SoS are at best only usable for making optimal use of Rapture ICD as pointed out by Elerion, but at worst can actually be working against us (i.e. forcing us to re-apply WS debuff on the tank earlier than otherwise, with no net MPH or HPS gain to our rotation).

Perhaps it's worth considering if we should be so interested in reducing the WS debuff in the first place, if we're really only using shield for
1) absorbing heavy incoming damage,
2) As a sort of emergency heal when people are at low health,
3) maintaining the WS debuff for 5% crit,
4) Proccing rapture (Which "only" makes it a nearly mana-free absorb, not a net mana return as we're used to seeing)

Question is, in how many of those situations would there be a WS debuff on the target when we need to apply a shield?

*More throughput in single-target rotation due to shield on tank + BT hasted penance, pom, gheal is more throughput than a similar use of BT where the shield is thrown at an off-target because the tank had WS up)

Sorry if I'm just speculating here without math to back it up, but it seems to me that in practice, there really is no net gain from SoS. Or am I missing something?

GHeal should not be used over Heal with the only criteria being that it won't overheal. GHeal is used when you need to get a big chunk of health to someone because if you just give them a little, they will die or get close to dying within the next few hits.

Another way of putting it is that if their health is dropping faster than Heal can heal, then that's the job for GHeal. Any other time, Heal will be more efficient so it should be used even if the person you're healing is missing 50k HP. As long as he's not STILL losing health at a really rapid rate that Heal can't keep up with. Hope that made sense.

It's very, very close though. I'm at 90k (maybe a little over) when raiding. That's only about 1500 Int away, which should be met in the first tier or raids. Even at 90k, I'm getting back over 75% of the mana back which is still good. The real problem is the 12 second ICD of Rapture that makes SoS purely for mana procs pretty moot.

On the subject of your post / the quote you quoted...I have found shielding, while slightly less efficient than Heal and GHeal, to save many, many lives during raiding just as it did in WotLK.

Deleted.

I've gotten to the point where I'm fairly well geared for beginning raiding (most heroic gear, boe epics) and have had the opportunity to heal a 10 man for a few different bosses. Here are my experiences so far:

Originally, I was utilizing a SoS spec trying to use heal as much as possible. I thought that removing WS as fast as possible and getting another shield up would maximize tank survivability. However, I ran into a couple problems with this method. Heal would simply not keep the tank up for an extended length of time with a raid boss hitting him. It might make one rotation before another pw:shield and penance before I'd have to switch to either gheal or fall behind further because of spike damage and have to flash to save the tank. Eventually, I would just fall behind and observing recount after the fight, hps was painfully low.

Last night, however, I decided to dump all archangel/evangelism/SoS talent points in favor of a ToT gheal based spec for tank healing. The results (although only one night of data on a successful Halfus Wyrmbreaker kill and several sub 30% attempts on Valiona and Theralion) seemed promising and a vast improvement over a heal based tank healing spec and rotation.

I would open up with shield and pom on the pull and then cast gheal almost exclusively as my only "heal" spell. I would continue to use penance and shield on cd, and pom while on the move. I find that the 10% increased crit chance due to WS on the tank is more beneficial than the earlier re-application of pw:shield due to SoS. While grace on the tank provides this same effect, having ws provide it allows you the breathing room of using penance on a non-tank and not worrying about losing the extra crit change. Sure, you will lose grace if you cast penance off the tank and that is not ideal, but if the situation arises where you need to and the tank then needs a gheal, you still have an increased crit chance to proc DA before re-applying grace back to the tank with your next penance.

Another overlooked benefit of gheal rotations over heal rotations is the added time it gives you. Your casting time overall is less for the same amount of healing done. This is beneficial because it gives you time to spare extra shields on dps taking damage, a second tank, or even to regen before having to cast again. When you use a heal rotation, you are locked into casting almost 100% of the time and you still fall behind. With gheal you stay ahead of the damage and even have time to focus your attention elsewhere.

Up until now, I've been favoring haste as that is what the earliest reports said to go with. But from experimentation and thoughts from the last few points, I agree that crit is definitely better than haste now for tank healing. Mastery needs to not be looked at as increasing only power word: shield but more importantly as increasing Divine Aegis, which with gheal casting can get some significant shields (almost equal to or greater than power word shield from my observation, not math backing).

So now that crit is determined to be better than haste, what would the stat priority be like?

Intellect > Spirit > Mastery = Crit > Haste ?

With intellect and spirit being standard gear choices in the sense that as you upgrade gear, those will upgrade. The only choices being in trinkets and gems. And even then spirit has its cap based on your own mana usage per fight.

So should we maintain similar levels of mastery and crit as they play off each other, or should still favor mastery whenever possible, and supplement it with a sizable amount of crit?

I think you have the right idea switching from Penance/PW:S/Heal + SoS to Penance/Gheal + ToT, and your note about staying ahead of damage is very valid, and definitively important. Towards this end, I don't believe that more than 1/2 SoS currently warrants a place in the disc spec, and even that is questionable if you are moving towards 100% Gheal usage.

I wonder if anyone has a good way of tracking the internal cooldown of Rapture. I would be very interested in a mod that helps accomplish this.

For me, my biggest concern with mastery is that I cannot find a way to effectively utilize aegis procs from PoH. By the time I've casted my first PoH, in most cases the raid damage is over and my aegis procs fall off unused. This follows for direct heals cast on raid members following spike damage from unavoidable single target boss mechanics as well. I have attempted to tell our healers to leave a 10-15k health deficit so that I can heal preventatively, however there are so many HoTs and passive area heals that this is rarely accomplished. This leaves only Aegis on tank critical heals and PW:S every 12 seconds. Because critical strike benefits all of our heals, and I cannot find a way to derive benefits from Aegis on non-tanks, I currently believe Crit outweighs Mastery. I would caution that if you find yourself healing tanks primarily and focus very little on raid healing, then the disparity between Crit and Mastery will be reduced. With my raiding style in mind, I use the below priorities:

Intellect > Spirit >>> Crit > Mastery > Haste

Ah, I stand corrected. I'm sorry I missed that. I've updated my earlier responses as to not confuse people.