I can appreciate your feeling here and I agree that we could potentially push things a bit further between Acts. I think part of the problem is that we’re trying to create a geographically contiguous area, so you don’t end up with the dramatic shifts from greek grassland, to egyptian desert, to chinese mountains. Maybe we should have stuck to the ARPG mold of Act1 grassland, Act2 desert, Act3 jungle/swamp. 
We’ve tried to go back and put in some effort to create more pronounced differences between Act 1 and 2, where we could and we’re now making a more concerted effort to build in a more unique feel from the start in Act 3. Unfortunately, the mountain deeps was part of our effort to do something more dramatically different for a cave and apparently that didn’t impress.
Given that we needed a natural cave for part of the level progression, I’m not quite sure what more we could have done besides possibly creating all new rocks but, for the most part, those are covered up by stalagmites.
In general, I agree TQ had certain feature locations that really stood out because they had their own unique art sets that were never reused. The problem though is that on TQ we had a team of 10 artists and on GD we have 2 artists. There is just no way we can produce art on that level and given that we’ve got 2 guys on art, I think they’ve done a fantastic job.
On the other hand, I can’t help but think some of this is looking back with rose colored lenses. I went back and looked at TQ undergrounds and compare them GD just to try to figure out more objectively what we were lacking. Since we’re talking about caves here, I only looked at the cave type undergrounds, not any of the building dungeons. Here’s what we have in Act 1 and 2 in GD:
These are just wall pics with the environmental effects turned off, which, if they were on, I think would set them apart even further.
Here are the natural cave undergrounds in TQ Act 1, 2 and 3. Note that these are shots from the editor - if they look empty, its just because a lot of the UG floors are pretty bare.
In terms of more man-made undergrounds, in Act 1 TQ just has catacombs and the labyrinth. GD has house cellar, laboratory and jail. I think we’re also on par with TQ in terms of random monster camp art. Where we fall behind is the unique cultural themed art sets, like the Greek, Egyptian and Chinese cities, the unique places like the gardens of Babylon, Palace of Knossos, Great Wall, etc. We’ve got more coming and some of the stuff planned for Act 3 will be, at least in my opinion, very different from the first two Acts. So, I’m not really trying to say that the way you feel is wrong, I mean, if that’s your impression, then that’s what it is and we need to keep trying to improve that. In terms of expectation though, in terms of what we set out to do, I think we’re doing a decent job of it. The reality is just, we’re never going to out-art TQ in one game with 1/5 the artists. :undecided: