From my point of view, DLC is not a mistake, but it doesn't fit well with this type of game. Reverie and Resurrection were overpriced and somewhat lackluster. Then again, if they were a part of the regular game, they would likely seem misplaced or odd after the fight with Satan. If they had not had Satan and made the Land of the Necromancers second instead of last, things could have been better.
For example, you defeat Camilla (the Dark Lord of Vampires) and then all of a sudden the aura in the castle changes. Laura comes running in a panic screaming something like: "what have you done!!!!" She then tells Gabriel about the Forgotten One. At which point, the events of Reverie and Resurrection happen as they did in the DLC with the Forgotten One as the final boss of the game.
Now, does that sound better? It sure does to me. It even caters to those who thought that the castle was the best part of the game. Plus, it emphasizes the importance of the castle.
Going back to what I said about DLC not fitting this type of game, enough said. I mean when it's adding arenas multiplayer matches in FPS games, DLCs work. When it's additional storylines for games like Skyrim, DLCs work. When it's games with linear stories and gameplay, story-based DLCs don't seem to fit well. Reverie and Resurrection as they are, fall into this group.