Enemy melee attacks:
It turns out that you can categorize ALL non-Monstrosity enemy melee attacks in the game into these categories:
Bulwark’s shield bash attacks
Crusher’s attacks
Mauler’s attacks
Rager’s attacks
Every other non-Monstrosity melee attack, which I’ve labeled as “Lesser Enemy” attacks. ←- All attacks in this category cost the same amount of stamina to block on a given weapon. Are you trying to block with a Knife? Then on that same Knife, you’ll use the same amount of stamina to block a Scab Bruiser melee attack as you would a Dreg Gunner’s bayonet stab. Same applies to Scab Shooter bayonet stabs, Scab Gunner kicks, Tox Flamer kicks, Scab Bomber kicks, Dreg Shooter melee attacks, Poxwalker and Groaner melee attacks, etc. Even Bulwark non-shield bash attacks and Reaper kicks are interchangeable with a Groaner melee attack for our purposes.
Mutant grabs and Pox Hound pounces were not tested, since they count as unblockable grabs rather than proper blockable melee attacks.
Bulwark shield bashes are unique in that almost every melee weapon in the game gets guard broken (aka 100% stamina loss upon block) if you block the shield bash. Bulwarks tend to use this attack if you get extremely close to them, so be wary of getting too close when engaging them in melee. If, however, your melee weapon is capable of blocking the shield bash without getting immediately guard broken (namely: Psykers using the Kinetic Deflection feat, or the Ogryn shield), the game treats it like a Lesser Enemy attack. This makes me think that the Bulwark shield bash checks to see if it’s one of those specific weapons being used to block, and if it isn’t, then it immediately causes guard break. If it is one of those specific weapons, it simply functions as a Lesser Enemy attack.
Crushers seem to have 3 different types of attacks: the infamous overhead; a side-to-side swipe; and a kick or punch. They seem to prefer doing the kick/punch if you’re extremely close to them, and this attack costs more stamina to block than their side-to-side swipe. If you’re farther away, they seem to do an even mix of overheads and side-to-sides.
Ragers (both Dreg and Scab) seem to have 2 different types of attacks: a 4 or 5 hit combo, and a pair of faster attacks that cost more stamina to block. They seem to like doing the latter when you’re right up inside their hitbox. Beware that some hits in their 4/5-hit combo can hit you twice, with each of those two hits taking away stamina separately. You generally don’t want to be blocking Rager attacks if you can.
Maulers seem to have only two different attacks: a side-to-side swipe, and their overhead. Unlike Crushers, they don’t seem to have a third attack that they use to push you away when you get too close.
Don’t bother blocking overhead attacks from Crushers and Maulers. There is exactly one melee weapon in the game that can block an overhead from these lads without taking health damage through the block: the Ogryn Shield. Blocking overheads with your melee weapon accomplishes nothing, as far as I can tell, except make you lose stamina on top of health.