Right at the moment everything is easy mode, 5 of anything can do anything. If you have heirlooms you can watch TV and spam your dps key with your foot and do OK. Since you enjoy leveling I would level up teams of 5 of each class. Then when Legion hits and they change the flavor of the month you're all set.

As for healers, Disc priest seems to be the easiest to box for me. You keep everyone healed up while DPS'ing and just click a bubble or something once in awhile.

But again if you're just leveling you wont need that. Keep everyone in DPS spec or it will take longer.