I think the biggest issue with GW2's storyline is the same problem Blizzard had with Cataclysm's: A giant, evil dragon of doom and destruction does not make for a compelling villain.
Guild Wars 1 (with the exception of Nightfall) always had a primary antagonist in the form of a human villain, someone the player can relate to. Prophecies had the Vizier/Lich, Factions had Shiro, and Nightfall had Varesh as the face of Abbadon.
Guild Wars 2 just focuses on Zhaitan and his minions, yet the player never actually interacts with Zhaitan in any way. The storyline just feels a lot less compelling and interesting when you don't have a villain you're interacting with.
Hopefully Anet will learn from this in future story arcs and add some kind of humanoid villain to serve as the player's connection to the Ancient Dragons. Otherwise, it just becomes one big silly Dragon Hunt.
While I can't think of a good example, a faceless villain can work, but it has to be a very character based story if it's going to be interesting.
Actually, I just thought of a good example - Lord of the Rings. You never meet Sauron the entire story. They had Sarumon as a secondary face for a good portion of the story, but the big villain was nearly the same as having a Giant Evil Dragon of doom and destruction. And that Story was Amazing, because it had ingenious direction. --- http://i.imgur.com/Gel15.jpg http://www.youtube.com/watch?v=5GOZjlwIwfk&ob=av2e If you click my sig, make sure you watch at least 60 seconds.