I played the fight as holy both times we have downed it. I think holy is great for the fight, alot of stacking up which is nice. I used divine star for the fight due to the stacking and it was great (also good for helping the dps at the shield phase since we had some burst problems there). Divine hymn is great as always and I managed to get it off 3 times. Lightspring is a must (as always). I used PI due to need of burst healing + I experienced some minor mana issues. Used mind bender also.
Healing this fight is alot about mana management, dont heal if no need, let renew and other hots do the magic for you.
You have to stance dance a little also but I ended up staying most of my time in sanctuary due to the massive aoe healing
Having tried out both Holy and Disc for this on heroic, I can say that I MUCH prefer Disc. Holy is strong too, but on a fight with such predictable damage and damage that will kill people very fast I prefer to be proactive rather than reactive.
Disc cooldowns also line up nearly perfectly with all of Feng's major damaging abilities (Arcane Velocity, Epicenter, Draw Flame). This is assuming that your tanks are negating every other ability that he casts. For each ability that we do not negate, Spirit Shell is godly. Watch timers, get Spirit Shell up, and laugh at the damage. Keep in mind that there is a small window of error as your DBM timer will only show you Feng's cooldown, not his time-till-cast. This shouldn't matter too much due to the duration of SS (both the buff on you and the shield duration). PW:Barrier is also very useful for this fight, for obvious reasons.
Mana will be tight, especially during the Shield phase since the boss does a mana drain. This is what I do to keep mana:
- Mindbender on CD. Use it early, use it often, use a power aura/weak aura and cast it the second it's off CD.
- Try to Hymn twice. I hymn on the first transition from Arcane -> Shield and then try to squeeze another in towards the end (usually during a negated Draw Flame).
- Potion of Focus on any transition.
- External Cooldowns: If you have a Shadow Priest, try and have them hymn on a transition. If you are lucky enough to have a Resto Shaman, Mana Tide will of course be very helpful as well and can be used three times during the fight.