I.E. : a common raider is just another human being, not that tough, limbs can easily be dismembered from a high caliber weapon or with a heavy blade. Should be pretty easy to hurt them quick.
Now on the other hand with supermutants.. these "animals". Now they could take a beating without giving up. These studs have been around awhile, and seen everything from a more lurk to a death claw. Even after a dismemberment these creatures will continue to fight based off pain tolerances and not having a human concioused mind anymore.
Just a cool topic to discuss, asking whether is strays to far from tradition. Or a spark for someone to mod.