It's been a while since I played Dancer, but I'd say the reason they can't and shouldn't consolidate the procs is due to the nature of combos. I can't actually recall if Dancer combos are interrupted if you use the proc immediately, but if they are, then the order of using the skills has to be Combo > Proc. If they consolidate the buttons, this doesn't allow you to save procs(and also means they have to set each combo to also combo off the proc skill), and later on you will get a skill that causes you to gain every proc simultaneously, allowing you to do your highest damage GCDs outside of steps back to back in any order.