I'm a fan of unique battle systems (that's what I tried to do with my game) and I think this one is one of the better ones I've played.
At face value it felt like Rock-Paper-Scissors, but being able to weigh each option based on the enemy and your current state is where the strategic depth starts to show. Having to overcome enemy Defences also prevents a "Attack Only" strategy from being optimal (as was my initial assumption).
Well done.
If I could change anything, I would have the 3 rolls after selection play out automatically. Having to click on "Roll" didn't add much for me, and it just gave me the opportunity to accidentally click passed my next Setup Round.