Why is the aggro of enemies in the Temple so abnormally low?

It’s far lower than that of enemies in regular maps—you have to walk right up to them to draw their attention, forcing us to hunt for faint, hard-to-see enemies hidden in every corner.

It's not low, it's just effing weird. You have to find the last dude chilling in the corner despite you killing every other person in the room but as soon as the doors open the mobs from the other room start swarming in, sometimes including the boss of this room.