I have to wholeheartedly agree on the theme+flavour part. That must be my main gripe against roguelikes. Even ADOM, which is heavilly RP oriented, suffers from that problem. Most monsters are totally random. Ants with mummies of random races, goblinoids and humans and orcs and dogs and worms and all sorts of totally unrelated stuff.
What ties it all together? Nothing.
It's something that I've always had against a lot of D&D inspired stuff, and Incursion doesn't seem to be an exception, unfortunately. Inside a single, only-slightly-above-average-sized dungeon (or single dungeon-level), there's dwarves, piles of undead, goblinoids, humans and other random races.
When I read Halls of the Goblin King, I pictured a dungeon featuring mostly goblins, making a solid, "credible" theme. Too bad I was wrong