Back on live, I was one of the biggest boosters for Regen and right now.... It's fine. It's not as strong as other sets, but in the years that COH was offline, I had the opportunity to play other games and realized that games can be much more fun if you're not so overpowered all the time.
If Regen were to get reworked, here are three things I would do:
Replace Stalker/Brute/Scrapper Regen with Sentinel Regen
Buff all the powers that are only 1/2 enhanceable so that they are fully enhanceable at the correct mods for the AT
Give Fast Healing 10% Sm, Le, Toxic resist
That wouldn't give it the same potential as some other sets, but it would HELP (not eliminate) the alpha strike issue, and that's all you really need to do.