Originally Posted by
Zojha
I would imagine the same as tanks and healers: To meet the demands of an arbitrary role mechanic.
My suggestion would be a stepmania role: When the combat starts, music starts to play and you need to press the right notes, i.e. abilities as they show up. If you fail, you/your party takes increasing amounts of damage (up to insta-kill). In the breaks, you can deal damage yourself as filler. Dancer is predestined for that role.
Sure, one might ask oneself "But why take such a role with you into a group?" and the answer is simple: Because you have to. Same as with tanks and healers. You'll just wipe from the music damage if you don't, just as you wipe from the unavoidable damage if you don't take tanks/healers with