Balance is very bad in arenas. I love it for hurting people but it just has zero survivability with 3 melee on your face.
I can't think of class I just would not play with. Maybe shadow tanks. Maybe. We have two amazing shadow DPSers so I would still take them if they come back.
Commando heals might be very viable for arenas, and they have a decent DPS spec.
Scoundrels are the best healers by far, but we will see how their role as a DPS turns out.
Sentinels/Guardians/slinger.... uh of course.
Vanguard DPS seems to be getting some changes, and they are definitely more viable than shadow tanks at this point.