The game officially has zoned areas, and i think there should be areas that are vital to leveling up and items that cant be accessed without completing tough storyline quests.  FFXI did this and it worked out great, it forced even the most "I wanna get to max level fast" people to do at least half the normal storyline. I hope they do this.

I am guessing although I do not know for sure. That some of the Dungeons will have quests to open them.

They certainly make the world more interesting, although having read some of the books, it may be hard to implement in this universe.  The usual method of allowing access is through Gate guards (which is possible here) or portals (not really in AoC) and portal keys for them.  But if you don't know, you don't know, not much more to say.  just a suggestion lol