I feel like being able to edit your deck could fix the problem. Being able to remove the defense cards could fix the problem, especially once you get to the point of one defense card giving enough defense to block everything.
The issue I see with this is editing to the point where you have no cards left in the deck, rendering you unable to engage in combat at all. Maybe minor amounts of editing, but not loading the deck so heavily one way or the other to prevent decks that would actually break the game.
