I'd box.

Collection quests would be very easy: clear area and collect with priest, then collect with druid (flight form) while priest is waiting safely mounted in the air (if not in Dragonblight or Coldara

Playing those two together would require two buttons
PULL:
Cat: [@target] FFF
Disc Priest: [@Druid] PW:S
DPS:
Cat: castsequence [@target] Mangle, Rake, Rip
Disc Priest: [@Druidtarget] Smite
Pull next mob even if current mob is not dead, it will be soon

For elite mobs: just go bear.

I've just leveled a Druid (Feral) to 79, I'm kicking myself now for not having teamed him up with one of my priests, but leveling him was so much fun and was so easy and fast that that thought never occurred to me.