Your first problem is Natures Splendor.
Not worth the point for a Doomkin unless you really have the spare point.
Second is Imp MF/IS
Too much trouble.
Third is Balance of Power
If you aren't hit capped you aren't doing it right.
If you have mana problems, go into Intensity or Dreamstate, don't go into something as foolish as the Frenzy for PVE.
http://www.wowhead.com/?talent#0xRbhiIocdIVuRuZbxcub
Is what I'd do first hitting 80(intensity or dreamstate, whichever gives more mana)
http://www.wowhead.com/?talent#0xGbuiIocdIVuRuZbxczb
Raiding if you have absolutely no mana troubles.
I haven't played an oomkin since BC, so take my advice lightly.
If all else fails, Elitist Jerks.