For hammers and maces, Skull Crusher and Bone Breaker work exactly as intended. The problem is that what few NPCs there are that have armor ratings have pitiful ones, which is especially pronounced by the fact that leveled NPCs gain health upon getting stronger, not armor. An NPC in full Deadric armor (mind you, no such NPCs exist) would have a paltry 108 armor, which renders the perks rather useless.
Here's what UESP says about the axe-specific perks, Limbsplitter and Hack and Slash: "The bleeding effect of Hack and Slash depends on weapon material and skill level and lasts six seconds. However even a Daedric weapon used with level 3 of Hack and Slash will cause only 18 bleeding damage. While multiple bleeding effects stack, by the time you apply several of them the enemy will most likely already be dead."
While the axe perks perform the best of all weapon perks in terms of increasing damage, it is still a puny sum that's likely to go unnoticed at all levels. This is a point that has been brought up many a time before. The question is, when will it be addressed?



