Ive been running a paladin 1 resto shaman 3 elemental shaman for heroics. So far they have cleared all but rising sun last boss, shado pan last boss and i forget the name of the third, second last insect boss. The rest however have been very easy to box with this composition, some bosses i will run with 4 elemental shaman. ilevel on them all is 460 now.

Pvp i run 5 elemental shaman and they are pretty bad for me right now, but Pve they are a strong group.
They are extremely strong when in ascendance, i blow everything on a boss, couple have died by the time its over.

I think almost any group comp will work for mop heroics they are very easy. In cata you had to seriously over gear to be able to have any chance in heroics, now you can do most mop in just quest rewards.