Wen i have duel in fist fighting i never loose any vitality!, even if i do nothing, my opponent is trying to hit me but my vitality bar is always full!, WHY?...
no that the thing!, i can press wrong and he will go in animation trying to hit me, and then just cut off, after that again same i can press key combination!...
You might try changing resolutions or maybe even turn ubersampling on temporarily to see if that changes anything . I know that has worked for other things . Also are you using keyboard and mouse or controller ?