Borrowing an idea from Diablo 2 which i booted up after a few years away.
Give certain items a 'set bonus' when the full set is worn. Examples might be the mithril set (make the vest non rare! Its only +1 dam after all.) red dragon etc...
That would make the re-equip stuff better without improving any individual piece, it would also be possible to put a set bonus on some of the more 'average' rares, if you could define what would make up a set at least, as pieces tend to be more individual at higher ranks.
What this would do is bring lower end rares more into line with god sets, but only when somebody chose to wear a full set. There would always be a trade-off between wearing the full set for the bonus, and choosing items from different sets, or just individual items, to get specific stats.
