Interesting combat system. If it has a flaw, I think its that it strongly favors the player as they go first. Being able to go all in on attack, knowing you'll strike first and don't need to worry about getting hit back as they'll die first. It seems optimal to just be on the attack, unless you roll really bad.
If that's fine with you then that's fine :) I dont know if you'd want to add an initiative 'action' that you could invest dice into as well.
I do appreciate how range effects your ability to hit, especially how being up right next to each other is a -2 penalty.