The phantom arsonist, a case in point. Added nothing to the story, seemed to appear and vanish as quickly as it arrived and served no real purpose except that it was a distraction for the police and provided Dexter with someone to kill. At least Speltzer offered more than "random bad guy, that you have no connection with". When he trapped Dexter in his maze, and the way he almost overpowered Dexter was a great moment IMO.
Best bits were the confrontations with Matthews and La Guerta tbh. Except, that seemed to boil over with La Guerta telling Deb she would be investigating the ice truck killings, then nothing for 4 episodes (possibly more) and WHAM... she's convinced it's Dexter.
What does always make me smile though, are the twists and turns that you never expect, like the phone tracking on Deb and Dexter's phone, or how Dexter managed to set up La Guerta for attempting to catch him in the act. Classic Dexter moments.
For all the hype, I would have accepted Doakes coming back from the grave, if only because he is such an awesome character. The flashbacks were OK, but just seemed a bit meaningless. As mentioned, they never really gave us more information than we already knew. Yes, he thought Dexter was creepy, but because Dexter says a line that he read in a killer's journal, Doakes conclusively believes it's all an act. I don't buy that.
I do await how they're going to cover up the shooting though. Usually Dexter plans everything, but so far, these little loose ends are coming back to haunt him, and it's only a matter of time before Matthews finds something, or someone (Deb) lets the cat out of the bag. For example, Deb shoots La Guerta from outside the shipping container.. the entry wound and blood spatter would not be consistent of a shoot-off between Estrada and La Guerta, so either they bodge the evidence or make both bodies disappear. In doing the latter things WILL get interesting.
The rogue captain investigating Dexter gets found dead in a shipping container with the murderer of his mother, or she goes missing just as she gets close and accuses him of the crime. In both scenarios, it would heighten suspicion to epic proportions. If not for higher powers (Federal or just Matthews and his "friends") to get involved. A more fitting climax would have been to show Deb shoot, and fade to black - giving the illusion she shot Dexter, but also maintaining that it could also be La Guerta.
Sad to see Angel retire. He's the honest symbol of integrity in that department. No one else (apart from Mike Anderson or Doakes - both dead) has really shown themselves to be a decent person, that calls it down the line. Quinn is bent as a $10 bill, Mazuka is just weird and will do anything for a piece of ass, Deb is covering up more cracks than a painter and decorator and Matthews is retired. It's interesting.
Another thing too, I don't really feel the connection with Hannah. Yes, Dexter confided with her and has "let go" since meeting someone that he can connect with, but he barely sees his son as it is, has already told Deb about the dark passenger, which makes her not much more than a booty call and she's not even someone he can trust 100% either, since poisoning Deb either.