I'm pretty surprised at how this discussion has gone. Do that many people really think Super Strength was slam dunk, #1, the absolute best damage powerset during live City of Heroes?
By that much? It seems to be implied that this is well understood. I also don't think you can ever look at single powers in this game and call them "overpowered" - almost every set has a signature ability or two that in a vacuum is "overpowered".
In my opinion, the best move is to simply to try to get SS back to the state it was in live. Simply removing the defense portion of the debuff has one real effect: it makes super strength stronger at lower levels until Rage has enough cooldown to be stacked, at which point it's exactly the same. Also, you still want to do that even without it being required to get rid of the defense debuff anyway.
Even if the general view is that Super Strength is a bit too strong with an un-nerfed Rage, I don't think adding this huge downside is the answer. A lot of people's enjoyment of this game comes from the nostalgia of playing their old characters again, and this change is something that very strongly takes that away from some people. It can be made to work okay, a lot of things can, but this change is something that is a huge negative for some people and I think that sort of methodology is something that should be avoided. If anything, changes should be made to empower other things to match.
Alternatively, minor de-tuning of Rage will feel much less debilitating to old players and won't take away as much from them, even if numbers are slightly smaller - not to mention it's a much easier change to make.