I would love to see some different and neutral behavior from monsters. DM2 had loads of these, making each monster/creature encounter unique and different. Like the Thorn Beasts walking around and chewing grass, then hitting you if you get in the way or become agressive if you attack or bug them too much.
Or those nasty little thiefs stealing your stuff then running away and hides it.
And those pesky minions flying up/down ladders an opening doors to get to you and lob lightning bolts at you.
Or simply the fact that some creatures would actually try to step away as you lob a ball of fire at them.
The monsters in LoG are pretty much lacking any sort of behavior outside "run around like confused ants" and "attack the player".