I play as a Khajit Acrobat and I'm 14th level. My armor rating is -23, but it doesn't help at all! Every attack of every enemy hits me. I don't see any difference between AR 0 and AR -23. At first I thought "maybe that's how the game works", but then I saw some let's plays on youtube where some Nord spellsword with AR -9 (!) can avoid almost every attack! Besides in the manual it's said that "Acrobats deduct a certain percentage from their opponent’s base chance to hit when engaged in combat with them.", but that's not what I see when I play him.
However as long as I have 300-400 potions of healing per dungeon - I'm fine, but this is getting annoying.