It's like the ever reviled ship map from TFTD, any map with multiple vertical layers with complicated connections are chores. They are rarely difficult as the AI has as much trouble navigating them as you do. Open base maps like the Cybertek one where you capture a portal are much less of a hassle without becoming the spawn camping demo that so many maps can become.
Yeah, while sometimes they're good, one needs to be careful not to make it simply tiresome. At least it's not as crucial for important one-time missions, because they're one-time.
As for the AI pathing, a lot can be done with the terrain routes which determine how non-player units move when not engaged in combat; but it's very imprecise and an art of itself.