My team are all 65 now ( see sig ) I now wish i would have made a 5th shaman and i can say that my Paly is my targeter 99% of the time. What i mean by that is the 4 ele shams kill stuff so fast no tanking is needed while questing, so i just target with him hehe. I can already see with a combo of grounding totems, stoneclaw and other nifty shaman abilities that a 5th shaman would have been MUCH easier to grind both quests and instances with ( once they get elemental pet totems ) Since I came this far with my paly, ill just take him to 70 and then boost a 5th shaman.

A few things to think about. having them all ele means you will kill stuff super fast. 5xtotem of wrath=15 chance to crit and hit. They also have +damage totems and the gear will make you a critting madman! Even with 4 this is nutzo dps. But a 5th just makes it overkill! ( overkill is good )
The other thing to think about is if you have different specs, you will have to macro manage a lot more. In my case I will even lose a bit of dps because I will be forced to make one of my shaman resto to be able to heal my paly without taking agro or going OOM too fast. SO ill have a tank, healer+ 3DPS. 3 diferent macro set ups=more work. 5 ele shaman is the way to go, all ele speced. no need for "better" healing when shit dies that fast. Remember grounding totems... ele pets, and stoneclaw totems are " great" forms of CC IMO ( who says shaman have no cc, BAH! )