As a tank I will commend one of the healers. Unless I can tell they aren't even trying. As healer I commend the tank unless they were a real D-bag and some how managed to avoid a kick. As DPS then of course DPS gets my vote sometimes based on how friendly or how skilled they were sometimes based on how cute their glamour is.

But those aren't set in stone sometimes someone just really shines. Really friendly, really helpful, a healer that pulls everyone back from the edge of death, A Tank that's considerate with their pulls. you get the idea.