I have 5 hunters and I love it. I paused on them at 39 to get the WSG necklace, and to work on my shammies (since they had rest built up). Casters in PVP can't even cast 1.5 secs spells with 5 pets on them, let alone hunters shooting. I can throw my pets as a 60-70 yard grenade and the people die before they can even get 30 yards from me. Of course, there is no healing, so I chose Draenei for Gift of the Naaru. It works really well. Also, most rogues try to gank my main, so I use potions to help with that. It really is easy even with elite mobs, since after you get spirit bond (health regen) everyone gets health (pets and you). Also, I try to share aggro equally, so all pets have growl turned on. They bounce aggro around and they all get hurt equally, so no heals are really necessary. I use mixed pets to get buffs and debuffs (1 screech, 1 furious howl, 2 high DPS, 1 charge).

In short, I have had 0000 problems with 5 hunters and love it. Good luck with yours.