Pretty good game, well thought out mechanics. I was on the point of giving up after maybe 3 levels because it seemed pretty tedious and overly difficult, until I happened to unlock a combo - then another and another - and realised combos are crucial to progressing against tougher monsters. Maybe that could have been emphasised in the story/tutorial, that they have to work together not just attack individually.
The timing for attacking can be frustrating, when the action bar is filled just as an enemy attacks, and then while you're trying to get an action in the next enemy attacks... might be nice if you could queue actions while being attacked and/or while the bar is filling, to reduce angrily stabbing the keyboard. I found it awkward targeting allies for heals, which put me off trying the other characters' buffs. And the difficulty increase was a bit too steep for me, compared to character levelling.
So on the whole a very good game, but some little things made it not entirely fun to my mind, still interesting to play and I enjoyed trying to discover combos for a while.