When I'm sitting here brushing my teeths I came to think of what I wanted to see more of. First I come to think of Galakrond, the progenitor of dragonkind. I think there are only one quest involving his resting place when there could have been lots and lots of lore here. Secondly Azjol-Nerub ofcourse. Such a shame it only became a 10-minute HC. Third is all the random statues, monsters, skeletons and so on around the world. Like the big snake-like creature in Old Kingdom (you can see him from the platforms before prince Taldaram) or the huge skeleton in the sea south of Wyrmrest Temple.
So, what do you miss? What did you want to see more of?