I think it's definitely an issue that there are certain spots in a lot of zones that are pretty much never used at all. Like the Feast of Iron in Dravanian Forelands. That said, Gathering and "World" fate bosses usually keep the overworld fresh enough. Due to the nature of relying on Duty Finder and how freeflowing servers are in XIV, an old school overworld based MMO won't ever occur.

What's kinda sad to me about it is that because flying is in every zone now, the whole world is in a fly over state at endgame. They could stand to give us a reason to kill overworld monsters too, outside of daily hunts and sidequests.