I’ve been a fan of Fiona since Tidal, and Idler Wheel is my personal favorite of her discography. I think it’s also her most meticulously crafted record, both lyrically and musically.
Ken McCandless wrote a rather in depth feature about dark music a month ago on MeccaLecca.com that you might find worth checking out. http://meccalecca.com/blog/?p=7686
Cultus Sabbati and Demdike Stare are both really creative bands you could classify as “dark”
And Extra Life is really interesting, especially compared to these bands, many of which sound like Joy Division wannabes