Heres a trick for yeah, the level 62 Mistresses of doom in the Pools of aggonar
enslave the poor things and force them to summon Imps. The imp are normaly hostile and stay hostile, ill leave it up to you to think of things to do with a Demon that mass spawns little imps that will kill anyone.
The imps got about 900 hp, and fireball for 300-400. Its all fun and games till some one summons imps on your face!