I'm just curious.
I notice that in the Doomsday engine (Doomsday 2, last stable release), monsters that would normally stay in a particular room or sector in the vanilla games are far more aggressive and will actively leave the room, open doors, and hunt down the player.
As an example - Map 16 of Doom II - Suburbs:
In the vanilla game, you start in a small room, facing a few Imps. There's a Revenant on a platform outside, and an Archvile waiting for you outside. You kill the Imps, kill the Revenant, go outside. The Archvile acivates, you kill it, and run to the next building, open the door, and a large number of Imps are packed inside, which activate when you open the door.
But in Doomsday, the scenario goes something like this:
You start in the small room, kill the imps, kill the revenant.
The Archvile outside activates, and enters the room.
The Imps inside the next building activate, open the door, leave their original room, and start coming into the starting room.
This behaviour is not limited to this map alone, it happens on quite a few maps, though fortunately, not as much as it used to in previous versions of Doomsday (I remember doing Refuelling base on an older Doomsday, and all the monsters from every room came at you all at once as soon as you left the starting area - this no longer happens).
This isn't a problem per-se, but it does force you to play the game in a different way, and can be a bit less fun. For instance hitting all those dozens of tightly-packed Imps in Suburbs with a BFG shot after opening the door used to be a lot of fun. You can no longer do that.
So, question: Is this a deliberate design feature, or is it something that still needs to be ironed out?
I've noticed that it's most prevelant in Doom 2, but I've also occasionally noticed it in the other games as well.