All Tanks get a stance that turns them into a DPS
All Melee get a Stance that turns them into a Tank
Healers get a Stance that turns them into DPS
Casters get a stance that turn them into Healers
Bards songs have a duration and straight mana cost when cast and do not debuff the singer's damage. Multiple songs can be active at one time by using the old Everquest technique of "twisting" your songs.