No expert but I can give you some starting tips.
On DM you don't need both Shadow Punch and Smite, drop Shadow Punch is the usual view. Also you shouldn't need Dark Consumption, Power Sink already gives great end recovery and you have better AoE's in the Epics. With Elec Armour many don't take the T9 Power Surge, it's a big crash and arguably is rarely needed.
If you're looking for solid example builds I'd check out SS/ELEC on the brute forums and DM/Inv/Shield/SR from brute and scrapper forums. You can combine best of both to make a really powerful toon. I think you want to shoot for capped S/L defence with enough recharge to run good attack chains and have Energize and Power Sink popping fast.
Hope this helps, I also have a neglected 50 DM/Elec so I'd love to see an expert post a reply. Julius Seizure used to post great info on this combo but not so much lately.
I have been away showing all my love to my heroes and my lvl50 dark/electric/electric has been neglected. I tried playing around with few things testing out respect and found my self running short on slots very quickly.
Was getting everything in DM except Touch of Fear, everything in Electric armor, fighting boxing,touch,weave with hasten tossed in. In epic maybe just electric fence. Without breaking the bank getting purples and PvP sets I am open to suggestions. Biggest issue was running short on slots. I think the last to picks we CJ and dark consumption.
Suggestions .. MIDS has trouble running on PC.
Thanks .. AC Warrior on Champion