Apart from the known passive AI bugs, I can't really offer anything too specific. I can state that I've observed wierd behavior in terms of where the AI will defend when I siege it, and when it decides to pull back and abandon the walls and gates. The behavior is inconsistent, and sometimes it will pull back when in my view, it has a better chance of holding me off at the breach itself, based on my previous experiences.
Sadly, I've taken to autoresolving all of my v1.2unofficial battles due to the unit cohesion problems. (Yes I will try other unit sizes later)
Cheers

PS:
Bookmarks