I run Priest + 4 Hunters and it feels very powerful with the latest 3.0 changes. I blew through SLabs and SV without a hitch and am going to try the harder 70s soon as well. I'd guess I could pull of a heroic or two when I get the hang of it, and that's wearing mostly blue gear.

Really, any healer with Hunters could be viable, but I'd recommend either Priest or Shaman for the synergies and group heals.