@Warhammer - In general, I agree with you, but I think you left 2 things out. The one is the well-known "stand by tower and commit suicide" issue. I'm assuming CA has fixed this by now.

The other one would be the AIs complete lack of response to the player's movements. This can be seen in non-city assaults, when you can ride units around to flank the AI without it moving, but it is better illustrated in cities.

I'll give an example - I sieged a city, brought up 1 tower, and had 2 sap points. The sap points happened to be far away from the gate, so I moved my army to that location. As per default, the AI was guarding the gates, with the majority of troops by the "default" start location gate. So I did the sap points, collapsed 2 walls, and used the tower to storm a third. The AI did nothing. I walked my army right into the city. The AI did nothing. Only when I went to capture the tower did the AI attack, with the units on the wall. The unit on the ground stayed there and didn't move until I killed the wall defenders and took the tower. Then it went into the "march around uselessly" behaviour you mentioned above.

The AI needs to be able to react to what the player does. If it sees the majority of the player's army lined up by 2 sap points, it needs to move its army to the sap point to defend there. Defending the gate is useless if I'm not planning on assaulting it.

Bh