Speaking as an ex shaman myself, I just thought I would mention that I think the enhance spec gets alot better at higher levels. At least it did in earlier expansions, I havent actually played it much since wotlk. And if mana is a problem, it isnt THAT horrible of an idea to grab a couple "of the eagle" type items to boost your mana supply an appreciable amount. I look at it as like how my mage was way back in the day.
Out of curiosity have you played a mana using class since MOP?