Well as we all know Cataclysm prepatch 4.0.1 has made us feel like in the middle of a earthquake by introducing lots of change mechanics, forcing all players to reconsider gear, gemming choices, talent builds, game play/rotations and even their existence
, and yes....it is only the beginning. But don't worries I'm here to help you survive until December 7th. I have made this recompilation of serious information from various sources, let me clear, this is not a guide, i just feel like helping you with some initial guidance so you can develop your own play style without failure. -The next information is a recompilation from Hegen's guide: Healing Priest FAQ v4.0.1: Surviving until December, 7th from Elitist jerks plus some additional information from: Disc/Holy priests in 4.0.1 from Tinuninu's guide in Manaflask.com and off course my super awesome knowledge
(i haven't even tested the patch, but you know)-Ok first lets start with:
Assumptions
This information is based on some assumptions, that you must be aware of:
* Converted WotLK raiding gear seems to be overbudgeted in terms of int. We're going
to swim in mana, which will be fundamentally different at level 85.
* Since mana won't be an issue, and level 80 fights are spammy, we're going to focus on throughput.
* For smite builds, I assume not to use Holy Fire, because we don't have access
to the spirit->hit conversion in the shadow tree (lacking talent points) and thus
won't be hit-capped regarding Holy Fire. For this smite spam don't forget to always have your Divine Accuracy glyph on!!!.
* Make sure you go to your priest trainer of choice and learn Mastery. These is
considered a passive talent.
*On a side note: Shadow priests now will start spamming SW:D when a boss rich 25%, so you should keep an eye on they to ensure they doesn't kill by their own crits >>.
Living as a Discipline!
a) Important Gameplay Changes for level 80
* Disc has a new spell: *Power Word:Barrier*, though with a cooldown of 2 minutes. Be sure to try it out.
* "Heal" is our new, slow but cheap standard heal. However, it will be mostly useless for raiding at 80 where healing is frantic.
* Expect overall absorb by your shields to be lower, so you will probably need to use more direct heals.
* Holy Nova is now raid wide (technically it's now only based on proximity)
* The new DPS-based healing talent Atonement allows us to perform semi-targeted passive healing by doing damage. It may well be that at level 85 raiding, this becomes the dominant disc way to heal, but we don't really know yet.
* With these changes, it's not clear which healing roles you will be good at when raiding at level 80. Disc seems to be more suited to tank healing than before, but that's really designed for Cataclysm encounters, not frantic ICC fights, where tanks can drop in less than 3s. Healing based on atonement requires proximity of the healing targets to the dps target, so we're talking about tank and melee healing here. For raid healing, you'll have to look elsewhere.
*Inner Focus now only affects Flash heal, heal, Greater heal, PoH but now it only has a 45sec cd....Yes no more free divine hymns....

b) Talent build for Discipline priests
Discipline priests can choose between a pure healing spec and a dps spec that I
will subsequently call the Atonement spec, named by the talent that makes this spec
possible. In this FAQ, I will assume an Atonement spec.
Why? Overall, healing is going to be easy until Cataclysm hits. At the same time we're
already bored by the encounters, so I suggest to use the time to get some practice with
our new toys. For this purpose, I recommend a build containing the dps-related talents
and glyphs for effectively using Atonement while also learning to apply Power Word:Barrier.
Like this: Link
Note that this build will probably not be the most efficient one for raiding at 80, but
the one we learn most from for Cataclysm.
c) Q&A for Discipline builds
Q: Why no Strength of Soul?
A: WotLK raid content is very spammy. "Heal" is very slow and really designed for Cataclysm content,
so we won't use it a lot, and thus "Strength of Soul" shouldn't be an important talent.
Q: Why no Empowered Healing?
A: Since we mostly replace Heal by Smite, and also most Greater Heal by Penance, 2% haste
from Darkness looks like a better deal. Move the points from Darkness to Empowered Healing
if you find yourself using flash heal a lot.
Q: Why no Mental Agility?
A: Because it looks like we won't need the mana at 80 while also lacking talent points.
If you find you do need the mana, get 1 point from Inner Sanctum and 2 from Darkness.
Q: Why Dispell Magic as third major glyph?
A: There's not much else to take here and we actually do some dispelling. At 85 though,
The fear glyph looks very promising for running instances. It's just that nobody needs
fear in WotLK instances.
e) Gemming, Enchanting, Consumables
Due to the removal of our 6% haste talent and the nerf to Borrowed Time, we're not
as easily soft-capped regarding haste as in 3.3 and before. This makes haste far more
interesting to disc priests.
Now, for level 80, my suggestion is to stay with your gems and enchants as they are and
see how you do in actual raiding. Then adjust. Going for straight Int in order to gain both throughput and efficiency is a safe bet. However, you may able to increase your throughput by going for straight haste if you find yourself drowning in mana. For level 80, I would rule out spirit and crit as candidates for gemming, enchanting, and consumables.
f) Reforging
Since current raiding gear doesn't appear to have mastery rating, my suggestion is to
start by reforging for mastery rating. Mastery is efficiency and non-overhealing throughput
for all our non-utility spells, so let's get it here, preferably by reforging crit.
Note: If you want to continue using lots of shields, I suggest you reforge as much as you can to mastery. If you plan to mostly spam smite with some Penance in between, then it's obviously not as important, because increased dps from crit will also increase the amount healed. Mostly a gut feeling though, things depend a lot on what kind of healing style works now at 80.
Living as a Holy!
a) Important Gameplay Changes for level 80
* Chakra is our new ability to get into a healing mode where we are better at mode-specific healing tasks.
While we don't know how good it will be at 80, now is the time to get used to it. I'd say forget about the
"Heal" chakra in ICC at 80. Renew and possibly PoH chakra might do well.
* "Heal" is our new, slow but cheap standard heal. It will be used more at level 85, where healing should be less frantic.
* The Chakra state in combination with the Revelations talent transforms our new spell Holy Word:Chastis to a healing related ability. Like with the basic Chakra, use the time to familiarize yourself with it.
* Holy Nova is now raid wide (technically it's now only based on proximity)
* Lightwell is seriously good and can now be used without switching targets, plus an additional 40yard asses improve.
b) Talent build for Holy priests
Holy builds for level 80 don't have all that many options. There's too much important stuff in the Holy tree to try out, and some of the options we have require more points in disc (for example for GcD based shields) or shadow.
Like for disc, I suggest we use the time until Cataclysm to get acquainted with new stuff
instead of wringing every bit of possible efficiency or throughput for farm content.
Try this: Link
You can always play between some prime glyphs, renew and lightwell are a must, but you might choose between Prayer of Healing, Guardian Spirit and Flash heal for the last spot.
c) Q&A for Holy builds
Q: Why Surge of Lightl?
A: WotLK raid content is very spammy. "Heal" is very slow and really designed for Cataclysm content, so we won't use it a lot, and thus "Surge of Light" won't see that much use. That said, we want to get a feel for things, and holy priest used to have real lull phases in fights (as opposed to disc), so let's find out. Also, holy priests might use Heal more than Disc due to Holy Word:Serenity making it safer.
Q: Why no Spirit of Redemption?
A: The spirit bonus is gone, and priests dying often enough for the talent to matter are a disgrace.This is a PvP talent now.
Q: Why Body&Soul?
A: Because you make everyone's happy if you do. Seriously, it's an amazing talent for
priests who delight in bringing the most benefit to their raid overall. If you didn't use
it so far, now is the time to try it out. If you find you don't get the hang of it, then by all means put it away in Cataclysm.
Q: Why Dispell Magic as third major glyph?
A: There's not much else to take here and we actually do some dispelling. At 85 though,
The fear glyph looks very promising for running instances. It's just that nobody needs
fear in WotLK instances.
Q: But I need more mana
A: The choice between efficiency and throughput talents in the build is really a guess.
If you do run out of mana, switch to 2/2 Veiled Shadows (1 point from Darkness, 1 from
Twin Disciplines). Next, move the remaining 2 points from TD to Mental Agility. Note that if your playstyle is using Renew a lot, MA may be more mana than VS, in which case you should go 3/3 MA first.
e) Gemming, Enchanting, Consumables
For level 80, my suggestion is to stay with your gems and enchants as they are and
see how you do in actual raiding. Then adjust. Going for straight Int in order to gain both throughput and efficiency is a safe bet. However, you may able to increase your throughput by going for straight haste if you find yourself drowning in mana.
f) Reforging
Since current raiding gear doesn't appear to have mastery rating, my suggestion is to
start by reforging for mastery rating. This is mostly to find out how good it is. I can imagine a lot of overhealing coming from it, but overhealing from HoTs is brutal in ICC with the 30% aura, so I'm not sure if that means something at this point, it will definitely will be a all other concept for when cata comes out, but since then you can take out all that mastery if you didn't like the idea of overhealing.
That's it by now.
Please feel free to comment your opinion, of course this information is still unstable because of the constant updates and changes, but at lest its a start. Share with us your experience so you can help us understand this all new concept.
Hugs and Bites, Noar.