Both characters grate on my nerves and make it worse because I cant shut them up.
True, they're both tied to quests, especially Maven what with her connection to the thieves guild.
But it was wasted potential because killing Maven could have been the start of an alternative questline to go to war against the Thieves guild in Riften. She was their biggest client, who loses a large resource if you destroy the Dark Brotherhood, but she makes pretty much no reaction to despite the fact that she kills her employees just for not acting like they love her enough(meaning she's a pretty spiteful woman.)