Holy Priests maintain a 50%~ healing contribution from Essence of Dreams once the buff has become active. This means if your PoH heals 5 people for 10k then it will add 50k of healing into the 'pot' of healing for that second, which will then be spread over the raid once that second has ended. Holy Priests and Resto Shamans are the only specs which get their full toolkit replicated by Essence of Dreams (where EoD amounts to a 50% contribution, while the other 3 healers get around 40-45% due to mechanic exclusions such as shields).

I do not mean to imply that those 2 specs must always get the green buff as obviously it depends on your healing setup - only that those 2 get the highest gain from it. The best advice is to look at parses for when all 3 buffs are active (generally the 4-6 min mark) and compare the output of the respective specs/buffs used and see what provides the highest output for each person in that period.

Holy is better on Spine. If you compare straight Gheal spam on different targets, Disc only surpasses Holy's Gheal numbers with 3 stacks of Grace. On constant switching of targets to single target heal, Holy in Serenity provides stronger single target throughput, especially considering the reduced time on Serenity's cooldown now.

I do. But I'm amongst the others on the task of outhealing the debuff. So I run in Chakra:Serenity and heal, heal, heal. As an additional bonus, I can cast 2 heavy divine hymns during the fight which also helps.

No it's not. since you have Penance ready for every targetswitch you instantly have 3xgrace on your current target and get full benefit for every GH (and additionally shield the target from incoming dmg while he cannot be healed due to the healabsorb shield being active). SO I think Disc is stronger on spine (at least in 10m).

Running a Disc+Holy priest on Spine seems to be proving very worthwhile in regards to 25 man. Disc priests are the only ones who will prevent a death, or essentially "heal" the person who's starting to get too low from damage with Searing Plasma ticking away on them. IIRC the only other healer capable of healing said players is the resto shamans totem.

Being able to utilize the holy priests shorter hymn during aoe damage phases helps my raid stabilize. Realistically neither of the two specs can be under utilized in this fight, unless you're running with all holy pallys.

With regards to heroic mode, the synergy here will only prove to be even more worthwhile.

On 10m Spine I played disc on week 1, and holy on week 2, and to our healer setup (paladin, druid, priest) holy seemed better in terms of how fast the three of us could get rid of the debuff and divine hymn was a decent substitute for barrier when we were doing a barrel roll. Though now that I think of it we did go with 3 healers since none had a dps OS and we didn't want to waste time on hearthing, respeccing and summoning back since it was late Tuesday night. :P So this might not be the best example.

I normally always play disc where possible, my whole gear is tended towards disc (less spirit etc) however in DS I've found myself playing holy on heroic Hagara (divine hymns for lightning phase, guardian spirit+lifegrip for focused assaults, PoH/CoH that heal people in ice tombs, body and soul for speedbubbles), and normal Blackhorn, Spine and Madness and found it viable.

That was basically the entirety of my thinking when I thought about it, and when I posed the question. There's no doubt that holy's raw output is going to be preferable for actually removing the debuff because DA doesn't help there. But effectively shielding someone(s) who are debuffed when you expect other damage to go out is irreplaceable. That some people opt for holy first is interesting. I would never run two discs in a 25 there, but it still seems like it brings more potential value to the table initially. Others disagree. Cool.

Holy also has Test of Faith (3/3) that it essentially becomes a Grace for those less that 50% health. The added advantage is that this 12% healing bonus is always on the targets with low health, which arguably should be the targets you are healing. There is no need for waiting for Penance CD to switch.

Also it seems as if Divine Hymn is a much stronger CD than Power Word: Barrier.

I'd like to know your opinion regarding Maw of the Dragonlord vs Scalpel of Unrelenting Agony.
I was lucky enough to grab the Maw in the first ID and to get the Scalpel on our Yor'sahj Heroic first kill. Since then I've sometimes struggled which one is better on a per boss basis.
I'm raiding 10 man and I'm not sure if the procc from Maw is worth it if only 5 people will be hit by the procc. On some fights (Ultraxion Heroic being the prime example) the Maw does up to 10% of my total healing but on others like Morchok I mostly go with the Scalpel because I value the haste more than the procc on 5 people which may not always be in range for it to even get hit.
Has anyone done some napkin math (or perhaps even a thorough analysis) of how much the procc needs to heal in order to be worth more than the secondary stats provided by the Scalpel? Otherwise I'd be glad to get some opinions on which bosses you (would) use the maw or the scalpel.

Thanks in advance

Good time of the day. We reached problems on Zonozz 10 HM.
Our setup: DisPriest, Rshammy, Hpally.
Our problem:When we are reaching Black Phase TENTACLE DISCO PARTY after 7 ticks of ball.
Who knows: 5 eyes, 1 big tentacle, 2 small tentacles.
Our camp: 2 melees(myself adk and awarrior) are hitting eyes, discipline priest stands between us. She is unable to heal us. She is using Pain Suppression on war|herself, I'm using AMS, but in the end of the phace someone of us is dying. She is trying to use Binding Heal. However she mentioned that her DCbuild is not absorption-based.
May I ask you to point us on mistakes in setup or provide a build and in-depth strategy for black phace?
Our log: World of Logs - Real Time Raid Analysis
Our priest:Блумелла @ Ashenvale - Game - World of Warcraft

We did it that way:
All go under big tentacle and get aoe heals. Ranged DPSers kill Eyes, Melee dpsers after stable their hp, go and kill eyes too.
I did that encounter as Disc Priest and every time get 1st place on WoL (by now its 4th, but I dont heal it anymore till last year).
I turned on PI and Jaws of Defeated and spam shield on all people while I running to our heal spot before black phase. PoM on cd, Rapture on cd, PoH all other time. We rotated some raid CD every black phase
1) HPal cds (wings+DF+valk), Rsham totem + Shield Spam with PI+JotD
2) Tranq+Dhymn
3) PWB + Shield spam
Thats all I think.