Really cool concept and very entertaining little game! With more polish and work you could really publish it commercially. I have a few minor criticisms:

• The font is a little intelligible at times.
• The first few combats are boring before you get the dice with cool effects
• A tutorial would be nice, it's kind of confusing at first. UI could use a little more work to show information more clearly too.
• Healing enemies are very annoying. They slow combat down to a crawl if you don't have any high damage dice.
• If I understand the mechanics correctly, each die goes through a progression of values. If they don't reset at the end of battle, that basically means that the optimal strategy is delaying victory until your dice are in the best state possible at the beginning of the next fight. Which is busywork.