2 words: Chain Lightning. 2 more words: Elemental Mastery. 1 Shaman is overpowered as it is, 5 of them can oneshot most elites then bolt/shock what's left before they ever get hit; kiting is key on some bosses, or designating one a tank with more tank-based gear than the rest use for dps, and since all 5 can heal + 5 healing stream totems you shouldn't have too big an issue; let alone when you get Earth Ele totems to temp-tank.