Maybe a class specialized on debuffs or a class specialized an fast movement (like sprinting on 4 directions repeatedly) with some skills that requires speed, adding more damage according to the speed, or a class that leaves decoys that give a large ammount of aggro, maybe a class that uses AoE skills (maybe like the Dryad's Blessing, but with more damage), or a class that uses fallen stars as a catalyst for some skills, like making stars fall or a special buff for all allies that changes depending the moon phase, it would be nice a "vampire" class too, like some hp-draining skills.
I just had some ideas. If you like them that's good, i you don't, that's good too.