Electric, IMOO. If you go the close range route for short circuit (which if you take electric epic you should) then you get one more aoe drain in power sink.
Every spawn you should be able to Short + EMP or Short + power sink if you slot for enough recharge, plus it gives you a third single target hold AND thunderstrike which is really nice. You can play like a pseudo controller with that much hold mag and all the draining.
My TA/Elec just hit 50 and she does pretty well with small spawns solo or in a large group taking forward assault with the drain.
Also, Thunderous + 1 blue + short circuit + power sink = totally drained group and full end.
Wow, there are actually two TA/Electrics in existance?
I kid, but that's a combo I've never actually seen. 
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I'm slowly working on one also. So far it's awesome sauce! Even at lvl 18!
"every defender needs to fight. I don't care if you have to use BRAWL!"
I persoanlly like debuff+ Oil Slick Arrow +Ball Lightning= Most enemies defeated (EB's and AV's whole other can of worms) or in groups really injured (Like say with a tanker... so a team of 2 in the Abandoned Sewers, doing fine..)
So I'd say while the combination sounds odd ( really TA fits my concept, work with what you have kinda thing) It's pretty close to what some have been asking in terms of TA/Fire (I imagine when fire eventually comes to defenders that they will play fairly close, probably fire defeating foes slightly faster)
Any other opinions?
Yeah looking at Power Sink, it is tempting have a Stalker that has it and is amazing. And Thunder Strike is tempting, but will also consider taking Short Circuit (might respec out Aim or Sentinel or make an alternate build that takes out Group Fly, again concept reasons, as he wouldn't be one of my imaginery childhood superheroes if he couldn't do that.)
Just got my hero to lvl 40 and I am now wanting to plan out my epic power pool picks. Now taking a look at the wiki I'm torn between Power and Electricity power pools for my defender nut I'm lokking for thoguht on any of the pools.
My Defender is a TA/Elec with Flight and Fitness pools already selected (so about 6 power choices not from my primary/secondary)