If you must run 4 huntes, I would say to go with either a shammy for the ChainHeal on the pets. Id would also only run one with a taunt unless you have multiple mobs. speaking on a lock composition team, when the pet dies, you have to have taunt ready on the other pet and stop all damage if you don't want the mob to come over and beat the mt pet's master to death before swapping to another pet.

prayer of mending on a priest requires damage to occur before it pops its heal and goes to the next target. issue isn't on the first pop, its on the second, third, forth, etc since you can't always guarentee that that target will take damage. If your pets are taunting around like crazy, this wouldn't be an issue though. roll with a renew ticking after combat and aggro sustained, but against some mobs, you are just going to have issues with a non-tank class, if not while you lvl, when you hit max lvl and then attempt content at lvl. blizzard screws entirely with the cap thresholds the second you go from 84.999 to lvl 85 that will be particularly painful.

anyway, best of luck lvl'in :P