I play on controller and so far everything more or less fits into 2 bars, with a bit of overflow into my L2+R2 for things like Limit Break, Raise, or stances. I dislike doing R2>L2 and L2>R2 because I know I'll fumble them when needed. So that's 40 buttons I'm comfortable with. Any more bars and I lose the ability to just tap R1 to swap instantly. I probably could get used to opening it up some, but I think this is a decent system.

I have it generally set up with healing/tanking/single target on bar 1, DPS/DPS/AoE on bar 2. It's not hard and fast, with some abilities doubling up, or having to overflow into the other one due to space issues, but that's more or less the philosophy I go into it with. So far Scholar is the only one that I can't do this with and have resorted to having things like Place/Heel on the W-crossbar. It's one of the reasons SCH is my least played healer.