I didn't run into much trouble with 5x lvl 15 shamans -- so I didn't have a fancy strategy or anything. I don't think there is a way around those packs. As I recall they would have a caster (always kill it first), a vw, and 2-3 other melee mobs -- are all linked.

Basically I killed the caster first with lightning bolt, threw out a few stoneclaw totems to grab aggro from the other mobs, and then dropped 5 fire nova totems. The stoneclaws grabbed aggro and the fire novas got the pack to about half life. I didn't have a problem keeping my team alive while picking the mobs off one by one after that.

hope that helped