During combat with crowds of enemies, it's much easier to string together combos if you just let go of the left analog stick and focus on getting the timing right on X/Y/A. Nilin seems to have an idea of "current target" that stays locked (even between dodges) until you move her towards a different enemy. I'm playing on a PC with a 360 controller, but I assume that there's a KB/M equivalent.
My other tip would be to constantly remix your combos; some enemy types are way easier to take out using the S-Pressens (especially some of the bosses), so focusing on cooldown reduction helps a lot. Other times, raw damage or regen may be what you want.