So I am in Rivellon, and Damian has revealed himself to me, and we fight.

He suddenly jumped 9 levels higher than he was before to level 42 (I am 33), and I cannot hit him at all, except for no damage. I am a Crossbow archer. I unlearned pretty much all my skills, and filled up on Accuracy, Point-Blank damage, Critical Hits, and I am using Power Arrows.

I do NOT feel like drudging through the remaining 3 Battlefield Dungeons (I didn't find the key to the level 6 one in Act 4), which might not even get me TWO levels worth of experience.

Apparently I am supposed to win this fight, as I just get a game over when I die. Yet this seems to be impossible. Explain.