Why the DK? I can see death grip being very handy, but wouldn't one shaman's grounding totem ruin that benefit? Given the number of wizard cleave teams I would think DG would often be useless. However, obviously DK is a great choice... can anyone explain why?

Instead of the DK, how about:

How about a lock for the AoE stun?

Enhancement shaman for the purge, grounding totem, and melee buffs?

Feral druid for MotW, heals on crit, extra crit, stuns?