This is a really cool concept! You should definitely keep tinkering with this, because even without the deckbuilding it had good replayability and with it I could see playing this for hours. My one recommendation is that you should be able to discard your active card too because I sometimes would defeat all enemies around me, have a block be active, then go find a new enemy and the first thing is block when I would have preferred slashing or healing on the way.