I can't view your spec from work, so my response may be pretty useless, but I can tell you that I would try and mess around with Shadow. Five mind blasts would be pretty cool, as well as following it up with five mind flays, though the Blasts may kill 'em in one shot, anyway.

Mana may be an issue, but that's one of the reasons why I have a mage team at 80. I can provide water for all of my toons. haha.