The DF outside of PVP does not make this differentiation and neither do most players.
It is 3 Tanks, 3 Healers, and 7 DPS.
You do not isolate a whole category of players unless you want the DF queues to suffer. Besides, it is unfair for healer and tank players if all the new classes are always DPS classes, same effect on the reverse, but to a lesser degree because everyone and their dog plays DPS.
