It seems that the Holy Smite(2 damage spell) card isn't taken into consideration in default mode. I had it in my hand, with 8 gems, and had 6 damage on the board vs 8 health for my opponent(lethal) but the bot attacked a minion instead with the minion and didn't cast the spell at all, ever. My opponent did not have a taunt on deck, the game should have been over but it lasted 3 more turns(still won).