I believe all heroics except Oculus have been cleared by the following teams:

Pally Tank, 4 Elemental Shaman
DK Tank, 4 Elemental Shaman
Pally Tank, Resto Shaman, 3 Elemental Shaman
Pally Tank, Resto Shaman, Boomkin, 2 Elemental Shaman

Allthough other various combinatinos are making serious progress.

So go with what works and pick one of those comps. I myself run Pally Tank, Resto Shaman, 3 Elemental Shaman and have cleared all but 2 bosses outside Oculus. In hindsight, I'd probably add a boomkin for the additional spell damage from their earth and moon talent but I don't feel like leveling one. DK's can also provide this benefit from their Ebon Plaguebringer talent but I'm kind of partial to my pally. One of the warlock curses also adds this benifit.

As for dual-specs, don't hold your breath.

And lastly, both plans are BoE world drops as well as BoP drops from the last boss in Magisters' Terrace. Whether they drop in heroic or normal, I'm not sure. Can't seem to find anything that is definative.