I definitely think this season was better than season 3. As far as dexter trying to connect with someone..it seems like he finally has. I think he's convinced that he cannot do both things anymore. I do feel like his dark passenger was put to the side for Lumen's darkness. I mean, he killed and did everything more of a necessity and he let her do most of the killing. I think that makes it less about the ritual and more about correcting wrongness.
I wonder if it is fading in a way also?
The murkiness of where his Passenger stands now was done very well. It seems like the Passenger's bloodlust was satiated when he was helping Lumen, I guess through the act of murder by proxy. Watch Dexter's face when Lumen was talking to Chase on the table... that mix of admiration and excitement at her growth was great.
But now that Lumen's gone, I think the reset button will be hit. When he said he would take on her darkness, him saying that is less metaphorical than someone else saying that. Without her revenge to concentrate on, I think his own bloodlust will return.
As for the overall episode, I really liked the ending. It wrapped things up nicely (in both senses of that word), and tied up loose ends, just not too tightly. There are still aspects of this season that can be explored, should they choose to.
What happened with Dexter and Quinn was very close to what I predicted. Both had the opportunity to screw each other over, and both didn't for the same reason: Deb. Quinn's development as a character is coming along well. He's gone from a character who was just there, to someone who actually impacted the plot.
The Deb / Dexter and Lumen situation was great. In the later episodes, it was clear Deb understood 13's motivations, as well as her partner's. Her decision to let them go was surprising, but not ridiculous, since her logic had been set up in previous episodes.
This season was up and down for me. The first half was a bit rocky, but the second half was absolutely fantastic.
It's tough to order the seasons, because some had aspects I really liked. Season two had a great Doakes storyline, but I never loved the Lila aspect. If I had to order, I'd say: 1, 4, 3, 2, 5.
But I wound up really liking this season, so "last place" is merely by default, not an indication that it wasn't good.
/long ass post.