There is no kill order that will make door open instantly, so stop saying that.
1 mob bugs out and doesnt spawn always and makes you wait for timer on door.
Killed all mobs to door, 14, got in the door 5 spawned,2 ghostly, 3 archers.
Killed them all, door opened.
Next run, killed same amount, 14 mobs.
Got in door, 4 mobs spawned, 2 ghostly, 2 archers.
Killed them all, door didnt open.