mobs above tunnel to tov aggroing through wall
 

sitting at tov entrance mobs from above can agro through the cave wall, travala, burrowers etc.

Outdoor zones do not have LoS checks for aggro. You'll see this happen in many outdoor areas

PoHate for example, you'll get aggro through the walls of any building and if end up going too high (gravity flux) you'll aggro the second floor