There's a problem with making content difficult though and that is that theres a huge number of incompetent players. The other issue is that dungeons are fun for the first X number of times you run them, but when you start getting into double digits it's no longer fun. This is where incompetence and repetitiveness would compound to create a really frustrating experience.
Sure struggling through a difficult dungeon is fun the first time, but can you imagine doing it over and over? This game is molded out of repetition. Whether this design was due to the fact the game had to have a really fast makeover when 1.xx flopped and the repetition is to buy them time to make the expansion, or whether the expansion will just be more of the same, who knows?