I really like the idea of the (original) Dark Brotherhood, and it's still my favorite faction to date, but Astrid turned the Sanctuary into a bunch of cutthroats and bandits, essentially. I'm not sorry she's dead, but I don't like that there's so little to be done with the Dawnstar Sanctuary. With Astrid out of the way and a Listener back in place, I hoped that we actually got to rebuild The Dark Brotherhood and be what it was supposed to be - a structured cult with it's own rules and traditions. But back to your question, I've never tried disbanding it myself - it just didn't seem worth it and none of my characters are so morally upright that they'd seek out the assassins with such a small reward. I'd either join it or just not touch it altogether.