This was previously reported in 3.x and seemed to be worse in PotD.  However, now I'm getting this behavior on Veteran.  For example, I aggro any group in a hallway of the Forgotten Catacombs and as a result I get the entire dungeon on my head.

 

This is starting to get a bit annoying -- all for a challenge, but...

 

Let me know if you need a save game (I have one at the entrance to the map in question).

I aggro any mob on the Nemnok lower level, i literally get ALL the mobs swarming to me. 

Same for Flooded Cave - aggro one mob near the entrance, ALL the mobs come running from across the map even corners I can't see.

 

Is this working as intended?