Center mass 2v2
Game difficulty: Hard (applies only to single player?)
AI player skill: I forgot to check because I set game difficulty, but next time I entered lobby they were set to "Hard".
The AI performed a couple of weak or meaningless actions that might just be ok on "easy", but probably not "normal".
Utterly useless: AI played sabotage to prevent troopers from moving on an island with no adjacent land.
Essentially useless: AI reinforced an isolated island (already defended) even though all hostile naval units were on the other side of the map (about as far as possible). Also, that player was threatened at the mainland border, where the same reinforcements could have been delivered.
But, but... they're mine! -- When I am holding a conquered capital, maybe my ally should understand that the territories and units held by that side will be mine, and are not worth attacking unless for very good reasons. (Such as wanting to balance our power in the new world order without attacking me directly...)
Is the AI good at considering turn order? The better AI's should know when the turn order guarantees that an effect will/will not happen.
Strategy note: When you conquer capitals and subsequently act before the enemy (on the next turn), you can send small armies to intercept retaliations. These armies can retreat with slight casualties if any, and guarantee successful control of the capital. I have never seen the AI in position to do this, though. In Centre Mass I was able to win most battles by autoresolve. (I did also observe a trooper take down a juggernaught.)
Intercepting the recapturing forces allows you to kill fewer of them before they fall under your control, and they are also not located in the capital at the beginning of the next turn; could be a nice head start.