The only way I see ED being a good thing is if the base values of all powers are increased such that at a minimum they can still reach their six-slotted values from i5 (which was already nerf enough with all the global defense reductions and rampant lowering of resists) with 3 slots. For example, increase Resist Elements to a base that will still allow approximately 40% resist if 3 slotted with resistance enhancers. As a passive, there is nothing else to slot into the power, so this would not make it over-powered. It does however make it a limited power when compared to others that can take more than one type of useful enhancement, and so benefit by having more than three slots.
Has this been thought about?
TrueHero