I would put that at the feet of expected fatigue, there's only so much you can extract from the concept (unless turning it into a straight "cop" drama). The extreme season 2 cliffhanger wouldn't pay off ever (I don't mind, but I can get why people would be let down by either the solution that could never live up or glossing over the practical details would feel a bit cheated) and the S3 cliffhanger has shades of the series getting over convoluted and pandering to its own past. Also S3 struggled a bit, the whole supervillain thing was undercooked, maybe also trying to speed up the character development at the expense of the stories. I liked what they did with the Sherlock-Mycroft dynamic though.
EDIT : Reflecting on the last episode of S3, it definitely doesn't hold up to scrutiny and the writing is lazy there.
Fargo was pretty good. I read somewhere the series may be a counterpoint of the recent trends of having twisted protagonists (Dexter, Hannibal, Breaking Bad...) but whatever the intent it was refreshing to have genuinely good people being heroes and monstrous killers being shown for what they are. Memorable characters, good performances and I liked that the show opened some ultimately meaningless avenues or loose ends to emphazise how luck based and chaotic those extreme scenarios are.
