I did the holy trinity with pally and 4 shaman and yeah, it rocks. Though for Wrath I'm swapping 2 shaman for a mage and boomkin and I'm pretty happy with it so far (mage and druid only at 68 though). There's a lot of good group synergy, more buffs, zomg water!, and portals. Keeping 2 shaman still keeps me fear immune (tested, works) and helps with casters a bit, though admittedly not as good as 5 grounding totems.

Anyway, as much as I love boxing I still like to hop in 10 mans and play with others so having 4 seperate classes helps me bring whatever's needed to the table.

After this get to 80, or if I need to build up some rested, I'll start leveling group 2 just to have the toons at 80. This will be Prot warrior (or DK), holy priest, warlock, shaman, shaman.