Remember when Regen got nerfed 3 times in the span of less than a year in COH's first year as an MMO? Remember Statesman being caught faking evidence against regen to justify his hate against the set with a replay so obviously tampered with that it was embarassing? Remember him deleting the post and never posting on the forum again after he was caught?
Anyway, I have never seen a MMO where chasing this phantom entity of 'balance' has worked out. Nor have I ever seen a MMO praised for it's balance. Nor played for it. Granted, yes, to a point things must be attended to. Sets can't really be doing something it's archetype isn't supposed to be, but the larger issue is one simple question. How many people are playing it? That should tell you a lot about what needs to change than taking out your microscope to see if sets are completing missions 30 seconds too fast.
Also tidge is right. Diminishing returns on effort spent on balancing is worth minding. This is a MMO. Most of the way there is fine. If this were a proper PVP game, you'd be more bothered.