Perhaps they can incorporate a little of both? Dungeons can have an attunement requirement to enter. This can be done with a chain quest starting at your GC, that requires you to enter world dungeon areas in order to investigate or any other story driven incentive. Once completed you gain access to to the dungeons, and can participate in the world section of the dungeon as well.

The only problem I see with this set-up is people may not want to HAVE to do a pre-requisite to enter. But like I said, it's an idea and we can always change things, or add other peoples ideas to have something that works.