...debuff text obscure the attack timer? This is especially relevant on the ranger.
...the slime boss, a boss where it feels like you almost have to spam your cards as quick as possible (which actually probably isn't the case, since the ranger's dodge=1poison is what you really need, to clear everything/fast enough) actually slow you down when playing cards, since you need to manually target each 1hp slime?
...the game give you no time to evaluate cards, especially when so many things generate cards? (this really is an extended issue, more related to gameplay/speed required to succeed)
...the game not just automatically have the enemy stat-box displayed on the right,

Honestly, this game is real close to being fantastic; the art direction, music, and overall feel/everything are great - there's just some nuances that need work.

The gameplay itself though doesn't match the description; due to the strength enemies hit at, as well as the insane speed they end up getting; it's really a 'do you have X survival cards for the fight' and 'can you play your cards fast enough?' - more than any real decision making in combat.

Also, the ranger seems like the strongest character by far, due to his ability to simply ignore enemies for X seconds (especially once he gets +4 attack speed, and the card that 1attack=1dodge) - though maybe I'm missing something related to the other characters. Between the Corpse boss, and the Slime boss, he seems to have the real things necessary to actually survive any amount of time.