The funniest part of all this is how they don't bother to dodge magic much, i tested it and about the majority of magic spells, the enemy dosn't even care to dodge, a completely visible fireball, ice spear, coming at you and you don't dodge, but an arrow that really thin, in the middle of the dark you can dodge...
Another funny thing i noticed is that... they don't care what circustance it is to dodge it... Your still hidden? Dodge it. They're fighting someone? Dodge your arrow still. Going to get a backshot while they are looking for the one that's shoting at then? Acquire a sixth sense and dodge it... I really hope they take a look into this because it's just freaking annoying, not to mention most of the time it dosn't even make sense for then to know it's coming. Please tell there's at least a mod that removes this feature...

On the other side of it: I find it pretty easy to avoid NPCs arrows, but I guess that doesn't help you. 
. How can they do that?!?