Very Well Done
I often enjoy wasting a few minutes of time on a short, simple game like this. It does get a tad repetitive, especially at the boss I was just clicking as fast as I could because it was taking quite a while, but was still a great game. It's heavily based on luck, but it's also knowing how to use your abilities.
I would enjoy seeing this game expanded, maybe give each class an extra ability, and have there be 2-4 dungeons total you can go through (make them each a bit shorter so it's not too long).