I had a squad of wraiths with 70 dodge fighting a squad of mites with 66 aim. The mites kept swinging at the wraiths while the champion with the bow pelted them with arrows all day long. (The Krax champion provided the fortification.)
It seems that once an AI unit is next to a player it will just stand there and keep swinging at the unit it first attacked instead of maneuvering to get to better targets.
Mites: http://i.imgur.com/20zjVaK.jpg
Wraiths: http://i.imgur.com/Y9uZ4Xh.jpg
