I was massively disappointed by the DB in Skyrim. All the quests are way to simple, and there's only one way to go about them. When you got the quest to kill the emperor I thought that it might redeem the questline, but then they totally dropped the ball. Like, your going to kill the EMPEROR, they could have at least given more ways to do it, but no, you HAVE to pose as the cook, you HAVE to fall for the trap, then you HAVE to go swim onto the ship, and then he just lets you kill him. It was massively anti climactic. Then, when you, Nazir, and Babbette are rebuilding the DB, it would have been nice if they kept the questline going and added, I dunno, some actual characters? In general, it was just reeaaalllyyy shallow. Like, it's actually harder to kill the EMPEROR IN THE MIDDLE OF A TERRITORY REBELLING AGAINST HIM (meaning that he would be on his guard, as well as the Penatus) than his cousin at her wedding. Also, in Oblivion, you don't have to go through a quest that's obviously meant to put you in the Dark Brotherhood, so it's much more natural, as well as making more sense. Also, I think the "Fallen on hard times" thing for the Thieves guild and DB was just a really lazy excuse to not make the quests exciting. Why would the DB not be thriving in Skyrim, a chaotic land that's in active rebellion, where the could be used by both sides against each other, and where lawlessness abounds (forsworn, for example).