My conclusion from seeing 10 mans, and doing them with vyndree is:

Most viable tank - Paladin
HOWEVER, you ahve to wait until he is -really- overgeared. Otherwise threat/mitigation/mana issues will arise from tanking mobs that were intended to be cc'ed.

Second most viable - Druid
Less buttons, good threat and avoidance given on par gear with instance

Least viable - War
MICRO MANAGEMENT HELL - however can deal w many diff issues if you're pro. (like me )