First let me just say that PoE has been, so far, a stellar game, and this is mostly meant as constructive debate about potential improvements for the next iteration.
I am just making my way through defiance bay for the first time, and I remember reading an old blog post about content density, especially in comparison to BG2.
Now from what I remember, Athkatla was a bustling place, and this wasn't a turn off. You walk in to the Copper Coronet and you have so much stuff going on. You pick and choose what caters to your interests. Then there was BG1, where content was less dense, but you got the ENTIRE city, edges perfectly lined up from one zone to another. There were so many random little houses and corners which you could poke around in.
I guess in PoE, the cramped wilderness areas had already foreshadowed the issue somewhat. I mean you go to the first wilderness area from the initial starting zone and you are basically confined to walk a very narrow and short path through it. You got inaccessible cliffs and a little grassy area and you are done. In itself it's not a big deal, but there are so few of the areas in total. Still, I was eagerly anticipating reaching the first major city to see what it would have in store.
Now to give you a summary of the feel: I'm walking through the administrative centre, and there's just 3 buildings you can enter! And not much is going on in any one of them. I'm sure there are some tie-ins with future quest-specific reasons to visit, but the general pattern is each building has 1-3 people with actual names, and then a bunch of generic NPCs who all say the same rotation of phrases. Another example is the major inn at the city. There's barely anything of interest going on, and compare that with BG2's major inns. The net effect is when you go on a tour of the environment, it feels a bit dead, at least in comparison to the games I mentioned (and even Planescape).
To sum it up, I would say that not only is the scale somewhat diminished (which is understandable given the development challenges), but the content could definitely be more densely packed in the environments that were actually fleshed out.