From media I've seen that I can't link here, this is actually a level 15 dungeon, not a level 20 dungeon. I think they went in with a higher level group just so they could show more of the dungeon and speed up the battles, similarly to what they did with the Levequest video.
This isn't breaking NDA, because this detail is in the beta roadmap: Level sync is not yet implemented. I don't think this is a level 20 dungeon, but the characters are at level cap.
Blahblah instanced dungeons
1.0 had tons of non-instanced dungeons. Many were beastmen strongholds, with very tough mobs that dropped coffer keys. They were tiered (bronze silver gold key) and some great stuff would come out of these coffers.
Many of us would regularly solo to farm the bronze key from Natalan to get a chance at Sentinel's armguards because they were the **** and sold well, and were meldable, which made for really great gear. If you wanted higher tiered chests you needed at least 4 if not 8 just to get past the gates in the stronghold, not to mention kill the nms that held them.
These interactions existed in 1.0, I see no reason for them to instance everything. IN FACT, one of the MAIN reasons for 2.0 was because they HAD to instance many things that they would have rathered be open-world, but the graphics engine couldn't display more than 30-40 characters at a time.
One of the endgame events, Hamlet, was designed to be an open-world defense event, like Campaign or Besieged. The engine couldn't handle it so they had to make it an boring instance. They said this and more, that this would be open world in 2.0, etc, they would add additional ones like defending other cities, etc.
The value of instanced content is that the developers can create a contained experience. They can guarantee these enemies wont be killed by another party and tailor the difficulty. I think people should stop yelling 'fire' in a crowded movie theater. Edited, Dec 27th 2012 6:37pm by Louiscool