Mostly the same stuff that people have already said:
RI slotted for -ToHit is your best defensive power. Don't bother slotting for -Def, it's already huge enough that you're autohit against the levels of mobs that you're getting solo.
EF is a damage amplifier. Apply early, and all your attacks hit harder. Just watch your blue. If you can't keep EF up and still blast away, then drop EF.
Slot AM for max recharge, immediately.
As far as Elec, your bread and butter is the two AoE powers, Ball Lightning and Short Circuit. Slot Ball for pure DPS, slot Short for pure drain. Use them both as often as possible. Two Shorts will make the entire spawn stand around looking stupid, and it's pretty easy to get the recharge faster than the duration.
With Elec/Rad, you're going to be better off turning the level down and the mob count up. -1/x3 is going to be way more efficient than 0/x1 or 0/x2. All of your best powers are AoE, so you need to get to the point where you can leverage that.