I think low health should make a person be downed, like in The Last of Us multiplayer.

If you get damaged enough, you are downed. You cannot attack, you can only crawl. When in the down state, you are bleeding out and you must be either revived by a teammate, or you can sit there and bleed to death after a few seconds, or an opponent can come up to you and do a finishing execution.

They should do something similar in this game, getting enough consecutive hits will cause you to be downed or in a weak, slow state. You can still attack and defend, but your movements are slow. You can heal yourself slowly, or a teammate can heal you up (they will know because a heal icon will pop up next to you), and once you're fully patched up, you can continue.

But if you are fighting an opponent and they get you in the weak state, then they can choose to instantly execute you, which most of the time, that is what ends up happening.

Now aside from this, there should be a stamina system in this game. Throwing slash after slash should obviously make you a bit tired and exhausted, even with sprinting in that heavy armor. There definitely needs to be a stamina system that regains by itself, just like how it is in real life.

Just make sure everything is balanced.