I don't think you understand. Rage is a stronger self-buff than any other set gets. But Super Strength is not a better set than every other set is, because the advantages Rage gives are made up for by disadvantages elsewhere. Thus, balance.
I'm not sure Galaxy Brain's got data on Super Strength, since AFAIK he's only done those charts for Scrappers, Blasters, and Masterminds, none of which get Super Strength.