I think it is good as it is, it means that armies, quite realistically, can escape with a reasonable number of troops left if things go sideways. If a guy is just trying to stay alive, as in running for his life and protecting himself with his shield, then he is going to be hard to kill. The older games where you could just hoover up the fleeing enemy got this wrong. There is something very arcadey about destroying an army in a single battle and it generally only happens if the commander is absolutely incompetent and gets surrounded.