I don't know,but it seems to have something to do with the damage to player option.Regarless of it(1/4,1/2,full) that damage still appears(tested even on bandits that infect villages,they are very rare,but an occasional 11 damage appears).At 1/2 damage,other damages appear,but this value is still pretty often dealt.At full damage it's still there,but blows of 30 or 48 damage(from guns that is,the death knight crossbowmen) are possible.The death knights deal 13 damage instead of 11.The nature of the blow does not matter(I've even received 11 damage from a skeleton archer),nor does its number in a series of blows.It's purely random,and I tend to think that these blows are crits.
I have also tested with heroic health on,and it makes no difference.If it does matter,it's almost day 150.I can't remember when this issue started happening unfortunately.
Still happens on new game,a bandit hit me for 12 damage when i had 80 body armor,10 toughness and 4 defensive tactics,but it rarely happens.Crit maybe?Plus I got into this battle where I could go underwater,weird.
A farmer can hit me for 12 damage,i have vaegir armor and 80 head armor...