In a new article at Guild Wars 2, Grubb gives us insight into ArenaNet's philosophy behind dungeon building as well as the mechanics behind them. "When creating the dungeons, the team was faced with two seemingly exclusive desires: we wanted to tell a story with a set beginning, middle, and end, but we also wanted to create an instanced area that players could return to and enjoy in multiple ways," he writes.
The dungeons are connected by an overarching storyline about a former group of adventurers known as Destiny's Edge. By the time players are ready for these instances, they'll have been introduced to the band, their legacy, and the resulting breakup. Dungeon-diving will give players an opportunity to meet the members and perhaps bring them back together.
Grubb notes that the game is currently home to eight dungeons, all of which are level 35 or higher. In addition to the story mode, dungeons also offer up to three different exploration modes apiece that should significantly up the replay value on these instances.
You can read the introduction to Guild Wars 2's most deadly places on the official blog!