My biggest complaints about the battle system were the long GCD and the lack of combos feeling like combos.
Let me explain that..
When one ability is supposed to combo from another it should feel natural to do. But in the P2 system, the GCD was applied to everything and you ended up with:
Ability 1 -> GCD -> Ability 2 -> GCD -> Ability 1 etc
That doesn't really feel like a combo, and it isn't totally necessary since I can just spam Ability 1 and achieve much the same result. My proposal to them (others said this as well) was to change it so the GCD triggered by a combo ability didn't apply to subsequent entries in the combo but then those entries would have cooldowns in multiples of the GCD to prevent combo spamming.. you'd end up with something like this
Ability 1 -> Ability 2 (goes on GCDx2 cooldown) -> Ability 3 (goes on GCDx4 cooldown) -> GCD -> Ability 1 -> GCD -> Filler -> Reset combo
It allows for more variety in a dps rotation while, at the same time, making combos feel like they're actually combos.
Now Yoshi promised in this phase that he'd lowered the GCD, so we'll have to see how it feels now, but if there's still a huge gap between combo pieces I'm not sure what good that will do.