After I had gone over the wall where there is an ammo box and into the orchard, the horde came and I found myself fighting and then dying alone as all of the bots had decided to stay on top of the wall to take in the view. Although Sienna did offer some token fire support, all 3 preferred to remain where they were.
Sometimes the bots are unable to follow if one does not allow them enough time to catch up. However, since I always pause at the top of the wall, the above should not be applicable in this case.

