First things first, as far as changes go healing wise not much is different, so you can all take a deep breath of relief if you were as worried as me that healing would change as much as it did between Wrath and Cata. Admittedly we're "only" looking at the patch preceding the expansion so much can still change, but the way it looks now I am healing pretty much the same way I have the last couple of months. Holy looks and works pretty much exactly the way it has whereas discipline has been tweaked a little more towards the absorbtion style healing, which is very welcome in my book. Spirit Shell that was long said to be a Heal-version of shields has now turned into a cooldown which turns all your healing into absorbtion mechanics instead for 15 seconds. This is an awesome cooldown, that when used at the right time can cushion your raid just before a big hit - the way discipline used to do it back in Wrath.
Although healing looks and works about the same, things have changed of course. What the new talent system means, in essence, is that your spec of choice comes with preset skills suitable for that spec. Rather than making people play slightly different discipline or holy specs, they're throwing in all the good and/or necessary skills for that spec (like Train of Thought, Strength of Soul, Rapture for discipline). The choice comes in the new talent tree that works differently enough for me to not want to call it a talent tree really anymore (not in the way we know it anyway). Think Diablo 3 style - it will alter your pre-existing skills, or add a few new skills to change, or fit, your playstyle.
A perfect example is the choice between Mindbender and Power Word: Solace. On the one hand you have a mana return-skill that allows you to heal while gaining mana, but with a cooldown. On the other hand you have pretty much the opposite - a mana return-skill that requires you to dps to regain mana, but that can be used anytime. What you choose will not only depend on your playstyle, but probably also on the fight. A fight that requires heavy mana usage for short periods of the fight would probably work better with Solace, whereas a fight with steady mana usage throughout the fight will prefer Mindbender (I've chosen Mindbender for now).
The fact that you can change skill anytime simply by using a Dust of Disappearance and some clicking makes me think that Blizzard want us to swap playstyle within a spec more than ever before, and I am welcoming the idea.
Other changes of note include;
Hymn of Hope being holy priest exclusive. I've discussed this change before, somewhere, but essentially it makes total sense. With the 8 min cd it had for disc and shadow it didn't seem like it was something Blizzard really wanted us to use (it normally wasn't up for two consequitive tries for instance) but didn't really have the guts to remove either. They've finally made up their minds about this.
Rapture being based on spirit rather than intellect. I don't mind this change because hopefully this means that holy and discipline will move even closer stat wise, making it fully viable to swap between specs without gimping out too much on either one because of lack of a stat. As someone whos preferred discipline throughout Cata I've been intellect heavy and spirit weak, which gimped my holy healing somewhat. I've seen my Rapture procs half in mana return this patch. This means I will have to re-gear, but since I will do this anyway in MoP this isn't a problem at all.
Dispel now has an 8 sec cd. A change I do not mind, possibly to prevent the solo-dispeller syndrome we've seen in Cata, where a few healers are set to do all the dispelling throughout the fight (most notably on Spine).
Glyph of PoH has been changed. A lot of glyphs have been changed, but this one is one that strikes me the hardest because it has been completely removed and I really liked that glyph...
On the other hand we've finally gotten the Lightspring I have been nagging about since Wrath. It only heals people under 50% but I can still see it being a lot more useful during tense situations than the current Lightwell is, even in the click-friendliest of raids.
There are a ton of new glyphs that look potentially good - Will Glyph of Holy Nova finally bring Holy Nova properly into the game? Probably not. Glyph of Penance looks really interesting, allowing us to run while casting Penance but with the drawback of an added 20% mana cost, could be awesome in the right setting.
For the time being I've chosen
Glyph of PoM, Glyph of Lightspring and Glyph of Fade in my holy spec and
Glyph of Pom, Glyph of Inner Sanctum and Glyph of Fade in my disc spec.
All of which obviously is open to change at any point, a lot of things still need to be tested before anyone can say anything.
If you're curious about my talent choices (or whatever I should call them);
Void Tendrils, Body & Soul, Mindbender, Angelic Bulwark and Divine Insight in my holy spec.
Void Tendrils, Phantasm, Mindbender, Angelic Bulwark and Power Infusion in my disc spec.
My real struggle was between Twist of Fate, PI and Divine Insight as they all look very useful and good. I've chosen two differently to test them out, but I think they all come down to fight mechanics. ToF seems mostly useful for very intense healing fights, PI can come handy in any kind of fight and Divine Insight can come handy where you either want to throw a lot of shields on one target (disc) or need that extra push in aoe-healing (holy). Overall I am leaning towards PI being more useful because you can choose when you need that extra output (not to mention mana cost reduction), but on the other hand PI comes with a 2 min cd. A tough choice indeed.
I am looking forward to doing the first raid with the new skills, and even more to seeing how healing will change further in MoP. What do you think of the new changes?