Well I suspect some weapons bypass the "armour" skill. For example I got hit by a short sword for 4dmg, and then the brute switched to a club and that did 30dmg.
Oh and this brute also has a hammer, but I don't like the weapon much.. seems to get dodged constantly. I prefer another brute I have with "tornado of blows" and a flail.. she can be doing nothing all game and then just oneshot the other guy with 2-3x hitting for 50+ in one attack.
Example fight: