Hmm, maybe it was just the time I saw them then - misbehaving for their creator!
I played for about half an hour, and every time I'd go into the light house, there would be 1-2 eng bots struggling up that first ladder, get to the top and get stuck, then jump back down and repeat, until an axis bot went in and gunned them down. Once they got past the first ladder, they usually had no problems getting to the top, but that first ladder seemed to be the biggest issue.
Crapshoot did a really great job with Assualt, and really demostrates how to let the bots use even the most tricky ladders.