The mana drain isn't a big deal. The time we fought it we just ran the clerics down the hall a ways. The range of heals is bigger than the range of the AE mana drain if I remember right. Anyway, the mini-worms are the backbreaker. I think we were among the first people on the server to attack this mob so when we got it to like 10% and the MA died, the worms popped and caught us off-guard.
Oh well, live and learn. He's not terribly hard, I'm sure it could be killed with 2 smart groups.