I have this lowbie new char that is Disc and find it hard to keep high mana while some heavy AOE trash are going on.
I guess it is no much different from raiding with heavy AOE.
How I deal with it:
1. Since there is no heavy tank damage, he is not treated much differently, maybe an extra Penance or a shield (maybe shield is pushing it if it doesn't break for the mana)
2. Prayer of Mending. This appears to be powerful but sometimes unreliable. Not very unreliable when the AOE is very frequent though. (I noticed it doesn't work on shielded targets, that's a bit of a problem, sometimes)
3. Prayer of Healing. This appears to not be very efficient. It's the main thing that bugs me a bit. Its healing isn't spectacular (I hope it's not just the lowbie gear) and its mana consumption is generally a lot. [BTW, I thought of using an Atonement rotation but that usually works as a starter since on heavy AOE it appeaes not be enough (Especially if not all are stack close by, hunters etc.)]
What do you think? Is there something extra I miss (I'm almost certain I miss something, I don't know all the spells yet perfectly).
Ah, by the way. I consider Holy may be more "Powerful" in AOE mode but I haven't tried it a lot yet. Only thing that conserns me with this spec it's that it's not that much of a "Panic savior" due to weak or expensive shielding.
Holy Nova appears weak and a gimmick to me right now. Maybe only for very lowbie mobs or for expeptional cirmustances like a secondary healer for Ragnaros phase2 ads.