The first major flaw is Kirkwall itself. It's a remarkably tidy city by any standards. You barely see any litter in the streets or bits of trash as you wander around. It obviously is home to the most diligent cleaners in the history of Thedas - and probably even puts modern cities to shame in most cases. This is a lack of "trash detail" that pervades much of the game. Places get dirty unless they are cleaned, and this should occur to some degree even in the utopia that is a fantasy world in a computer game. It doesn't need to be brown and mucky everywhere (as would likely be realistic), but there needs to be some mess, otherwise it's simply not believable.
Obviously all mages are forced by the templars to master the "tidy floor" spell
Kirkwall's second problem is the fact that it doesn't change. DA2 takes place over 10 years, yet Kirkwall is almost static in appearance during that time. No new buildings are made, none fall into disrepair, the same tiles are missing in the stone walkways, the same cracks exist in building walls. While it would not be intelligent (or feasible) to redesign the city repeatedly each time a few years advance during the story, the fact that virtually nothing changes is utterly ridiculous. This is particularly the case after the second act, where the city is home to a full-blown conflict in the streets. Yet a few years later when the story resumes, the city has been rebuilt to an identical match of its former state. This is sheer laziness in terms of level design, and does not lend credibility to the narrative at all. Good level design should help tell the story of a location just as much as words should, so to flagrantly disregard this opportunity and to disrespect the storytelling of the game is a hideous shortcoming.
The poor quarter was rebuilt perfectly back the way it was? Seriously?
The third, and most commented on issue by DA2's critics in terms of level design, is the gross amount of level reuse present within the game. There are a few stock areas that you travel maybe a dozen times in the game, perhaps with different sections blocked off here and there, maybe sometimes in the other direction, but most distinctly copied and pasted wholesale. When part of the critical plot of a game sees you go through and area you've already explored several times before as part of a random cave, the impact of the story and the sense of adventure are all but lost. This is without doubt one of the most telling indictments that DA2 simply wasn't given enough time to be developed. No, level design is not everything, but to come up short in such an obvious fashion that is terribly grating to the player is either a sign of a rushed product, or design staff who simply didn't understand the gravity of the problem for the player. I'd hope it was the former rather than the latter.
However, the news isn't all bad, so I do want to finish with one "good news story" that came out of DA2: Sundermount. This section of the game, or rather, the exterior areas (because the internals are part of the set levels used ad-nauseum) of it, are one of the highlights of the level design. Of course, there's the natural draw of "mountains are pretty", but while Sundermount does succeed aesthetically in providing good visuals, part of this is due to the technical design. Simply put, it reuses existing level design properly - it uses it as backdrop. The foothills of the mountain and the lower parts can all be seen as part of the vista that you can survey as you climb. This is intelligent area reuse, as it not only provides a sense of achievement (because you've climbed those bits before), but also helps to contextualise the player's position and current progress.
If you look carefully, you can even see people walking down below
So the news isn't all bad for Dragon Age 2 on the level design front, but unfortunately it tells us far more about level design through what it does wrong than by what it does right. If there's interest, I might try and put together a few points about when, where and how to reuse levels in a way that's less jarring to players.