I've been thinking of a few different things.
First would be moving to an HP system--give the hero 10HP and monsters a lower HP. That would give you a head start in the beginning for sure.
Second, I could have them play poorly... take a random number of cards, don't take enough cards, stack the deck with low cards, etc. Bosses could play better--or even cheat.
Third, in true rogue-like fashion, I could give the monsters a chance to successfully attack, so even if they win, they may not do damage.
Open to ideas as well :)