[HoneyBadger]

The reason that crits sometimes appear so skewed sometimes, is because crits are more realistic-in their way-than hit points. Hit points represent the sum total of physical punishment a unit can recieve before it becomes a casualty, in a very abstract way. Crits, on the other hand, represent the factor that a unit might become wounded/disabled through extreme, penetrating damage.

To give an example: a jotun unit might have 25 hp, representing it's ability to function after taking enough normal damage to render harmless 2.5 10 hp. humans. Either unit, however, ceases to function after you cut off it's head, regardless of hp. That's where critical hits come into play.