elementals are in a very bad spot as far as mana goes. I would recommend dropping some dps and using more lightning bolt maybe?
Affliction wouldn't be a bad way to go as far as mana regen goes
As for the mage...I've heard frost is also viable...I don't know how true that is.

I wish I could give more advice, other than grab some better gear. I know the people that are clearing heroics are doing it with higher level gear than would otherwise be necessary.

I can't comment much further without speaking out my ass.