I have been watching the AI carefully, and have found that it has a very difficult time in keeping its unit's cohesion up. It seems like units are almost always in constant momvement, meaning that every turn each unit loses around 15 points (1 point is lost per day of movement for most formations). As turns move along AI units get lower and lower, to the point where large and effective formations have very little, if no, combat strength (have seen entire corps dragged down to single number values for unit strength).
I am going to try and severely cohesion loss for movement, representing cohesion to be solely battle condition of the troops. I have read of many formations fighting extremely well, even after hard marching. Since the AI tends to foul up its forces, while players are much more capable at 'resting' their forces before committing them to battle, that cohesion lost via movement (as it currently is) is just too strong.
Currently, most units have values of 100 (which equate into 100 / 100 = 1, meaning each day a unit keeps in motion they lose 1 cohesion point. 15 days / 1 turn equates upwards of 15 cohesion points lost per turn).
I am thinking of values of 20 (which equate into 20 / 100 = 0.2, meaning that after 5 days in motion, they lose 1 cohesion point. 15 days / 1 turn equates upwards of 3 cohesion points lost per turn).
This drastically reduces, but does not eliminate, cohesion loss that the AI tends to suffer from (while humans can deal with it much better, plus will make attacking slightly more worth while).