it's the same story as any zombie apocalypse movie/game,
survivors, desperate situation, lone survivor braves zombie hordes for his people.
tried and true setup, no reason to score it down for following this formula.
honestly, yes, it's a Beta, hence the creator's request for Feedback, which is in fact, something drastically different from whining or non-constructive criticism, give him/her something useful for improvement in the full game, e.g. a quality button to help framerates, rather than simply stating "game is slow"
you stop it from healing by stunning (unleash the Ice Sword or use Thunderbolt) or using Seal on it (WMagic or Unleash Rune Blade)
they even give that tip during the fight ^^