i use the druid and 4shaman combo its really good, spell synergy doesnt bother me too much, mash the keys and we're good.
the real cons i believe are:
MOTW, Moonkin aura > extra set of totems
There is no need for a 5th set of earth/fire elemental totems
Moonkin Form's +400% armor means that if you starfire, moonfire and insect swarm and wrath spam you can most often keep agro off your shamans, so for parts where mobs hit hard, like the gate keepers in mechanar it works as a very effective tank without wasting a earth elemental totem.
I love the combo for pvp and pve, but the only problem i find with PVP is the fact that when your getting a name for yourself in the bg everyone will often make sure they target the moonkin first.