I've looked around and it appears some others on steam have noticed this as well. In Sandbox mode (admittedly I haven't played anything but sandbox mode) the AI seems like it doesn't have a legitimate interest in attacking other factions. I have seen Aquitaine, over the course of a game year, take a single city. According to the ledger, nobody else has taken anything, while I have managed to conquer all my historical faction territory (playing as mediometrici) as well as take out half of the Treveri.
At other times, I'll notice the AI attack me with large numbers of units (6, 7 units) but none of them have any food and they break and run almost as soon as I engage them.
Any fix to these issues in the works?