Has anyone actually tried the combination of hunters+healer in pvp?
Hmm... world PvP, yes. Battlegrounds? no.

Keep in mind, my hunters are only lvl 68 since they're being parked until my priest/warlock group is 80.

I can tell you that my healer druid is ALWAYS the primary target. I can also tell you that I can't do the normal druid thing to save myself (I never did the Bear quest, so I have no bearform... I also can't cheetah run-around because my hunters are following me). Generally, as a defense, I sit my druid on a sh*tload of traps.

My hunters can kill pretty quickly as long as they have range (which is pretty easy now that I have leap-disengage). My druid CAN take a few hits, even in treeform.

I would say based on my experiences...
5x Shamans = easysauce PvP survivability.
1x prot paladin, 4x shaman = still pretty easy to PvP, particularly if they mistake the prot pally for holy (and I fake heal for this very purpose)
1x priest (CoH), 4x shaman = priest drops like a rock if it's melee, easysauce if it's a caster
1x priest (CoH), 4x warlocks (Aff) = Squishy, but I'll take you down with me even after I'm dead. Soulstones are less useful here since running all 5 back is usually less time than SS and rez.
1x priest (CoH), 3x warlocks (SL/FG), 1x warlock (Aff) = Priest dies. Always. However, with 4 soulstones I don't care. This is my preferred lock/priest set, and I've had a great time anti-ganking 80's.
1x druid, 4x hunter = Meh, 50/50. If they start at ranged I usually win, if they're up-close melee it's harder.

I would say, correctly specced I prefer (for PvP): Shamans, Warlocks, Hunters. Facing and range issues with hunters is just plain worse. HOWEVER, if I were looking at PvE I'd go: Hunters, Warlocks, Shaman. Warlock pets are teh suck for holding decent aggro and they take too much damage. Hunter pets are my FAVORITE for holding aggro and (at least as far as pets go) damage mitigation.

I'd say it's an even trade to say they're less viable in PvP, considering that Hunters are my preferred class for PvE.