I honestly feel Enigma is fine - the worse dungeon is the encounter in the Fallout reference, that forces you to play in turn-based mode, since that breaks the rules of the game on a whim. It's backer content, which sort of explains it, but the other backup content is better.
Anyway, Enigma isn't everyone's kind of dungeon - 100% agree, but it is a completely optional end-game dungeon. You don't need to do it, and I would not be surprised of most players playing without a walkthrough even find all 4 masks to access it. But then? The puzzles are hard, but logical (and definitely better than the 5 domino puzzles), and the end encounter is good as well. It's best to regard it as optional challenging content (I know I don't do it on every playthrough, and definitely didn't do it on my first one) similar to the Dave's Challenges in the Goldbox games.
I have some sympathy for people finding Chapter IV annoying due to the navigation and it is also hard on the frame rates - knowing how to get access to all the teleport locations and getting them early helps a lot, but admittedly that is not something that helps you on a first playthrough. For me that was compensated about the plot finally picking up - it's sort of where you get the feeling that it is really possible to 'solve' the world-wound problem.
