Go with 2 heals, think of this fight as the same as Baleroc or even Ultraxion for the healers. Basically 2 healing this fight not only:
a: makes it possible with average raid DPS
b: actually makes the fight simpler (due to tactics)
-You all stack on the boss, no exceptions (even priests, this isnt HC mode)
-1 healer and 2 dps into spirit realm, try not to get the same dps into the sprit realm each try (to maximise the buff they have from sprit realm on boss)
-Assign one person to call out exactly WHO is going into the spirit realm, I found a tank is the best person to do this simply due to the fact they have the easiest job on this fight! :P
-Be aware of the voodoo doll debuff timer, it generally clashes with the spirit totem, I found that the healer without the debuff will generally have to go inside the spirit realm twice in a row but you just have to adjust who goes inside the spirit realm accordingly as it happens just before the spirit totem finishes.
-Make sure the MT pops some defensive CD when voodoo, and the healer going into spirit realm helps aoe raid before going in.
-The healer going inside spirit realm>>>>heals him/herself FIRST (by this I mean just cast 1 single heal to proc the buff on yourself) and THEN spams heal the DPS asap, the more heals (even when dps are full) means the dps get more of a buff when leaving the realm, tell your healers to heal them self one last time JUST before leaving the realm to prolong their buff)
-The healer inside the realm ONCE everyone is full hp LEAVES the realm, there no need for him/her to be in there at that point (use voice comm to decide when to leave)
- Use BL when Frenzy starts (or just before if you don't get frenzy before 5:20secs into fight)
-Tanks need to save some big CD for frenzy and healers need to pop nice cds at this point, dps blow all they got
- Do not let anyone go inside the spirit realm when boss reaches about 23% (frenzy starts at 20%)
-Boss Kill gz
oh and btw you mentioned 11 players in your post, just go with your strongest dps, and make sure your dps/tanks help the healers out since this is a very healer dependent fight (and by that I mean the healers will have the most "stressful time", sure the dps need to output some good damage but its the healers job to "buff" their damage aswell as making sure no-one dies!)
Yes, you have to 2 heal it. Unless your DPS are godly.
Resto Druids seem to do the worst in the Spirit World (they don't stack the damage buff on people as well, and have less 'direct' heals, so it may be better to drop the druid healer.
We 3 heal it and have 2-3 awesome DPS and the rest average. I play resto and found the spirit realm rather simple. I saved my tree of life incarnation for when I'm in there, you should get a decent amount of stacks on the DPS. We 2 resto Druid and 1 disc priest healed this. We were about 20 seconds from the enrage timer.