This morning I was playing Brigandoom solo with Merisiel in the Woods location. Base game, no add-ons or gold purchased (yet!)
When fighting a Bandit henchman, she rolled an 11 against the Bandit's 8 yet took damage.
Later in the same game, she fought a shadow, rolled a 14 and took 3 damage.
I'm not seeing anything that would boost the difficulty, am I missing something?