Hits with a flail (damage range of 25-55) to the heads of bandits/brigands with bandanas (20 armour) often/typically do this (I got the same exact result twice in succession the other day):
– Brigand’s head armour hit for 20 damage and destroyed
– Brigand’s head hit for 11 damage
If the raw damage was 25, that would destroy the armour. Then, 30% of 25 is 7.5, and 150% of 7.5 (for critical damage on a hit to the head) is 11.25 …
Damn. You expect more from a menacingly spiked metal ball battering against a bandana.