I dislike the IO set system more than any other item or equipment system I've played in any game. To me it's: tedious, doesn't feel satisfying to pick up a single IO set piece or frankly even a set or two (you have to invest a lot to notice stat changes), doesn't allow me to leverage any new mechanics or abilities (I'm just a better "ball of stats" to slam against enemies), and it lead to the inevitable auction house that you have to partake hours in if you want to accumulate the large quantities of IO sets you'll need if you want to see substantial benefits. I do however like procs and globals, slot one and it does what it says on the tin, no other researching, Auction House hours, etc. required to see it work.
I don't feel CoH was ever balanced around IOs, I don't feel it currently is, and I really hope Homecoming Devs don't make the decision to do so.