To prevent as much confusion as possible, STATS are implemented to make the following abilities useful:
THE KING, Otyugh
Phase Salvager
Chrysaora
Maxwell's Demon
Purple Nymph
Graviton Firemaster*
Note that 0 HP does
not mean auto-death; otherwise, Phase Salvager is useless. Maxwell's Demon basically has an ability to kill any creature with high ATK, and if combined with Chrysaora's ability, may allow the civy to kill the Otyugh with their 'Paradox' skill (if the Otyugh is 'poisoned', it can't gain any additional HP with devours). Likewise, Phase Salvager can learn the stats of an individual to figure out what role they are, granted, it's far more difficult, but certainly somewhat interesting.
And to reiterate:
ATK and HP have no effect on voting whatsoever. It's just to make sure the above skills have some sort of 'flavor'. For example, if you have the Pharaoh role and the Otyugh mafia member tries to 'Devour' you the first night, the Devour skill fails (5 HP vs 9 HP), and you survive!
Likewise, the Purple Nymph in the game inverts ATK stats, so if a Phase Salvager player sees someone with negative ATK, they can automatically assume they were hit by the Purple Nymph skill.
EDIT: Leaf Dragon, Sapphire Charger -> Graviton Firemaster, and Massive Dragon skills have been edited/'swapped' for extra clarity/balance by the way.