Guess what? Game graphics! Wooooh!

[LoTekK]

Personally I think the bloodied version works better. You may not want to go with blood, but if you're going to take the effort to make different animations for different health states, it would probably be worth your while to differentiate noticeably between them (the previous low-health animation, to be honest, barely looked any different from the healthy one; in fact, if I hadn't read your post, I would have thought you accidentally posted the same images twice).

Some ideas to try in lieu of (or even to complement) the bloodied version:
tattered clothes, tired eyes, mussed up hair, a more horizontal, or even downward-pointing, orientation for the sword (to show he's tired).

[Zomby138]

although I really like the bloodied animation, you might want to bare in mind that if you're going with that then you're gunna have to make alternate version of every single animation for when he'd low on health, running, jumping, attacking etc, where as if you just go for looking tired then you can have alternate idle animation and keep the rest the same.

[Zolthorg]

I'd definately stick with the wobbly sword for the tired animatio and the more properly held for the normal idle.

You could opt for some sewat or keep tehe blood and tone it down to just dripping when tired if you don't want to have to replace the head in every animation when he's low on health.