The patch 2.0.8., one of the really bad mass beastmen spawns happened in front of me in the Screaming Bell on the location on the picture (taken in a later game). I guess the small level difference made the game think I couldn’t see them spawning. I haven’t just stumbled upon them when it started, I was there guarding that side because of the horde announcement, and they didn’t come from behind the fence. All the enemies coming from there spawned in front of me.
The mass was impressive, as usual.