Just caught up on this thread. I haven't been involved in the DDA scene for a while, but allow me to share my perspective on a few different things.
Bottom line (TL;DR): DDA played it too safe by copying too many elements of DD1, and it suffers from the exact same flaws that DD1 has. They had an opportunity to improve upon the original design of the game, but didn't.
Fun fact, when DD1 was very first released, nightmare difficulty was not initially on their roadmap. Due to the success of the game, they wanted to introduce more content, and more difficult content. However, there was a