2 tanks make this a lot easier, i don't think 1 tank is helpfull hint =p
make sure people are assisting to burn down one mob at a time. Have the warrior DPS disc for the add waves, and have the necros use life burn. The shaman should be dotting/nuking too. All pets should be active and have buffs + panther. The key to winning the encounter is to kill the add waves fast enough so you don't get overwhelmed.
I would suggest having the pally multi-tank mobs and give the warrior just the emp (pally live DPS is shit anyway.) When emp spawns, have cleric spam heal him and have the DPS burn him down. Have the shaman keep idol of malos up, so he can slow emp quickly on spawn, and go back to chain healing the pally. If things get really hard, have the pally kite.