Only thing that would prevent you using the gamepad is speed, but you must remember that there is gcd between every heal. So you have plenty of time to cycle to your next target while you are locked out. Sch does have the off gcd lazer heal, but I still don't feel like I'm too slow. Also if it really comes to it, you can use keyboard F-key targeting. I've also heard about people getting the little micro keyboard addon for the ps3 controller and binding it to use for instant targeting.

Experience reference: Was able to solo heal Titan HM after heart phase as whm on PS3.