This season was an absolute mess - not only in terms of the subplots, but in terms of the pacing. You could honestly just tell someone to watch episodes 1 and 13, because those are the only two episodes in this entire season that you would actually need to watch to know what's going on.
The pacing with the Rachel storyline was absolutely terrible. It took Doug 12 episodes simply to find out the general area in which Rachel was living, yet within one episode, he travels halfway around the world, intimidates Gavin, finds Rachel's specific location, travel's back to the other side of the world to Rachel's location, buys a van and tools, kidnaps her, drives her out to a remote location, digs her grave, decides to let her go, then changes his mind and kills her. These events should have been spaced out throughout the entirety of the season, not crammed into the last episode.
Claire's decisions throughout the film were also downright ridiculous. This was a character that was cunning, controlling, and manipulative during the first two seasons, and yet throughout this season, she was whiny, needy, and irrational. She begged Frank to engage in borderline illegal nepotic act so that she could be the UN Ambassador, only to fail miserably at the position which was topped off with publicly shaming Petrov in front of his country and destroying everything Frank had worked for. Then, she comes home, campaigns a bit, and after ~30 years, only then comes to the conclusion that the marriage isn't working out, and that the problem is Frank? Please. Frank gave her every opportunity to succeed, and she failed. She wanted more and wasn't satisfied, so she walks out on her husband of 30 years, the freaking President of the United States, in the middle of a heated campaign - when, two episodes ago (~5 weeks in the timeline of the plot) she was happily campaigning with him and had just renewed her vows. It just wasn't at all believable.
The rest of the subplots were completely pointless - Russia? Never amount to anything. America Works? They built it up for 8 episodes, it collapsed, and now its gone. We didn't see Frank's reaction to Jackie. Remy just packs up and quits. The Tom subplot was incredibly boring, yet even more irrelevant was all the time wasted with the Tom-Kate dynamic - no one cares.
The entire season was nothing but filler, and one thing was made incredibly clear - Netflix wants to milk this series for as long as possible.
If the writers want to give this series its mojo back, you do one thing - have Frank kill Claire through some sort of intermediary. He knows he can't win the 2016 election without Claire by his side, but if she's dead, he'll gain massive support via sympathy votes. It will be another "card" stacked on the house, and it will reinforce Frank as a rutheless thug who only cares about one thing and one thing only - his own power.