Fun and functional, but definitely not balanced. As you've noted, the Monk is absolutely busted. I definitely shouldn't have beaten this game on my first run, but once my strategy shifted to supporting the monk as he destroyed everything, that's what happened. Then again, it's impressive that this game is flexible enough to allow for that kind of strategy, even when it wasn't my plan starting our, and it was never TOO easy.
Since you're interested in updating and fixing stuff. I'd add that the enemies are typically a much bigger threat than the bosses, as they often do more damage than the bosses from my experience, come in groups, and drain resources that you can't recover easily.
(I'm up for doing a more in-depth review, but it would take time, since I would need to do several more runs to figure out the rest of the classes)