The only changes I've made to 4e so far:
I 'fixed' the psion. They get more damage dice for their at-wills as they hit higher tiers like everyone else gets now.
I added a +1w or damage die for paragon, and a +2w or damage dice for epic. Sorry, but I felt doing 1w+ ability mod at paragon wasn't enough, and getting an extra 1w at 21st level for at-wills wasn't enough either.
I allow PCs to up the damage of lower level encounter/daily powers instead of being forced to take another power as they level up.
I do these things because monsters have too many HP's. Also, monster damage goes up a step at paragon, and again at epic; yet PC damage doesn't really do that...in the RAW.
I'm also going to try the 13th age escalation die next time we play. That seems like something worth trying out.