It may take time to unlock content and the content may never be unlocked if you deliberately just grind xp through other means rather then experience the story but that's the intention and the design from the development team to encourage people to make sure they do the story and unlock these dungeons as a sort of unveiling and reward for getting there. Because it forces the player to unlock it before they can progress the story therefore there will always be people queuing for the dungeon. And such design helps in certain ways as well like controlling floods of noobs into the new expansion areas because only the ones who finishes the main story up till 2.55 are given access to Ishgard, which i think is great for now since it's just the 2nd expansion.