You're group shouldn't have any problems... our guild just 3-shotted it last night (with all but 1 healer never having fought it). First time, the two on the far side didn't switch evenly and Lady Blaumeux began spamming her AoE. Second time, the Ret Pally lagged and got gibbed standing in a void zone. We began with the following starting positions:
Thane Kor'thazz:
1 Resto Druid (the one that ran it before)
1 BM Hunter
1 Assassination Rogue
1 Blood DK
1 Destro Warlock
1 Prot Warrior