Very neat idea! It's like a reverse turn-based game, where instead of you controlling the order of damage, the number is already there! The complexity is very enjoyable. And everything I thought is definitely OP somehow already not OP. Like I thought I'm definitely safe with 5 blocks per action until the enemy deals 12 dmg on 1. Very clever usage of dice and conditions of attacks/blockings. The creator must have really thought this through.
As for what I think could be changed, maybe the atmosphere looks kind of plain? Not sure how to describe it. The monster and all the pixel looks really cool, so good choice there. Maybe it's because none of the sprites really stand out because everything looks dark? But with the current way, the important UIs and numbers stand out just right already. Hmmm. not sure.
Overall, very very nicely done! Lov'in it!