I have to agree with the original poster. I want to play the heroic line in the game. I'm not interested in the dark brotherhood or even the thieves guild. In oblivion I didn't finish the Shattered Isle DLC because I didn't see a white line through the quest. Like the original poster, I don't object to dark quest lines in the game but I do want a heroic line as well.
if you didn't attempt to trigger the DB quest line then you've missed out on a lot of heroics. That's what I love about Bethesda---you always have a choice. After seeking out the DB the first time, you have the option to take the high and mighty road by flat out rejecting to join it. At that point, you'd get the opportunity to crusade and anhilate all of the Nocturnal's diabolic brood from Skyrim for good.

