I'm sorry to hear you quit. What part did you find difficult? Also what other feedback should I include for damage? I thought the numbers popping up after hitting the right buttons or the Groovy popping up after long combos would be enough. I clearly need more feedback if its a problem, though.
I didn't notice the numbers at first, and to be honest, I found the first fight already difficult : the arrow are fast, and you must have all of them. Maybe you could just make fight easier (slower arrow, monsters with less life) and add a sound feedback ?