For me, the whole "wounds that would incapacitate a normal human" is just a Space Marine thing though. A Guardsman gets his hand cut off they're pretty much dead whereas an Astartes immediately starts to clot the wound thanks to their enhancements. Heck, the Iron Hands literally do it as an initiation rite.
For CSM like Berzerkers or Plague Marines, they've got the normal Astartes toughness plus Warp blessings. Being blessed by Khorne doesn't necessarily mean you're invincible or whatever but you might get enhanced reflexes, speed, or strength that would give you that extra edge in combat vs a normal Astartes. At least that's my reading on it.