My 'default' for all my Brutes is the Energy mastery pool. Since you don't have many slots and will only have room for 2 powers, I'd suggest Superior Conditioning and Physical Perfection. Even as a /elec more END is always nice and its a chance to slot 2 more Performance Shifter Procs (or a nice Health proc like a Regenerative Tissue +Regen).
Beyond that, I will suggest Leviathan Mastery- having 2 cones will really help DB.. locking mobs in place for your AoEs. Also- Arctic Breath's -Def -Res will compliment the Weaken combo and just Ablating Strike by itself. Mu Mastery's Elec Fences and Ball Lightining would achieve the same (locking in place) and may be better "themed" with your Elec armor.
Stay AWAY from Mace Mastery though.. the last thing you need is another Redraw....
"Well, there's going to be some light music and a short note of apology saying, 'The universe ended last week, we're really sorry, we don't know what you're doing here, didn't you get the message?'"- Steve Moffat
See, I was going to go with Superior Conditioning and Physical Perfection, but my one friend was all "no, you already have a heal and an end drain, go get something else, like Soul!"
I don't have end problems with Power Sink, though, so would Focused Accuracy be any good?
I have a DB/Elec nearing 40... and I'm torn as to what Epic pool. Ancillary, Patron, doesn't matter.
Most characters I have an idea based on theme or abilities, but here I'm lost.
A slight issue is that I won't have very many slots to put into anything, and I also only have room for 2 powers.
Any ideas?