One way that I think that the AI can be made better in defense is to allow it to actually take up defensive positions after a point is completed.
What often ends up happening is that once a point is completed (captured/destroyed/defended) rushers run to the next point before the AI can get into position. So instead of pushing against an AI defense, the point is mostly taken by the time the AI shows up and makes a token show of resistance.
The solution IMO is to have a "regroup" period of about 30 seconds to 1 minute after each point where the restricted zones would remain the same. During this period, the AI would be able to respawn and take up defensive positions while the players would have the opportunity to resupply. Only once this period is over would the restricted zones shift and allow the players to push to the next point.
This would both make the AI better at defense (by allowing them to actually get into position to defend) and mitigate the all to rampant rushing by ensuring that rushers can't just waltz up to a point without encountering proper resistance.