Without seeing your build, or knowing what your goals with the character are, it' hard to say what the "best" epic for you is.
However, Mace Mastery is worth considering: Scorpion Shield gives a nice chunk of Smashing/Lethal/Energy defense, and Web Envelope is an AoE Immob, which will help keep things in your AoEs - Especially Rain of Fire, which normally causes horrible scatter.
@Roderick
RoF used to be really bad as in making everything run out of it, but it has changed. Not sure when they did it, but there is a slow element in it now. When I cast RoF, everything gets the full damage of that power so a immobilize power would not be all that helpful as it did before the change.
Scorpion Shield sounds nice though. That would add to the DEF from the Combat Jumping I have now.
Since the fire blaster in an AoE AT, many of these pools are not making much sense to me. Can anyone come up with the correct solution and why?