I just couldn't do this guy with my prot pally + 4 shamans. I used the spot in the pic above - its above the room next to moroes, where all the dancing people usually are - and the shamans never got hit by the balls, but he would basically get to 30-35% and heal up to 40% always, just bouncing between those two numbers. Very frustrating as you can imagine, wiped 3 times after spending 20+ mins getting him to 40%.

What I did was port my pally back to shattrah and spam trade for caster DPS, filled up the group with 5 more mages/boomkins and 1 shotted him no problem. Everyone got the bat, my pally got the axe (woot), and everyone got the quest done. Went on with the group and did maiden/opera before I had to leave for lunch.

So I'd recommend you solo perhaps attumen/moroes/maiden, zone out for 30-60 mins so the instance is cleared, and then spam trade/lfg for casters only to do just the new optional boss. They can pretty much go all out DPS, I just used my shamans to chain heal (one of the boomkins died). Boss dies fast with a bloodlust and 8-9 DPS casters, lol

Oh, just have your tank kite him around in the room below, keeping away from red orbs. They heal him when they explode, the range is funny though because some that are super far away still healed him when I was soloing it. Have everyone go up onto the pillar ledge in the room above, and the bombs will never come close. You can't do it in the room above moroes, the bombs spawn up there.