I miss the feeling of seeing more dangerous high-level areas that you can't get to yet. Being a Lv5 newbie looking down the path from North Shroud's beginner area at the Lv25 banemites ready to eat me alive if I cross the bridge, or peering through the tide gates in western La Noscea to the Sahagin base. It's there to be entered, if only I were strong enough.

Somewhat contrastingly, I also miss non-aggressive enemies. Obviously the further in you get, it's appropriate that there are more things trying to kill you, but there's no reason for everything to be. Passive enemies, where logical, make more sense and add to the world. There's no reason for butterflies to be attacking you viciously.