I get why others say you can completely skip this season and not miss a thing but I disagree as I think you'd end up missing important character development for a few characters. This is without the benefit of hindsight of course so it could all end up meaning diddlysquat in future seasons.
Dexter putting himself out there for another person in beating up that abusive parent, finding love again, and seeing someone overcome their "Dark Passenger". Quinn loving Debra enough not to land Dexter, a guy he wouldn't hesitate to get at, in the thick of it. Aster(?) coming to terms with Rita's death, making up with Dex, and just her general character in being there for her friend and having a mouth that would put Deb to shame now. Harry being proud of Dex beating up that abusive parent, admitting he never thought he (Dex) had it in him to put someone else first. I know it's not much for a whole season, but it's still something.
I really don't know why they ended it the way they did with Lumen leaving as it just rendered the whole thing as a waste of time. It helped Dexters character development a bit, but I don't think that was enough to warrant it. If they had ended it with Dex and Lumen becoming a couple (and partners in crime) with them both trying to juggle becoming a family with Harrison, Cody and Aster(?) coming home along with catching bad guys together as a couple going into next season I think it'd have been fine, and I'm really disappointed they didn't go down that route as I thought Dex and Lumen worked well together.
The whole thing with Deb letting them run off was annoying, too. I saw it coming and got the reasoning behind it, but surely she would've wanted to see who the couple actually were? It might've been too soon for Deb to find out about Dex's life but I think that's the way it should've gone having already ended up in that situation whether it'd have been premature in the story arc or not.
A couple of other things I want to get off my chest are that this whole Quinn being suspicious of Dex storyline only makes me miss Doakes as he was a much better character than Quinn, and Stan, the detective Quinn hired to investigate Dex, was hilarious and died too soon. I honestly couldn't buy him as "Pohleece" as he just reeked of villiany! What a voice the man had. That was another annoying thing in that his investigation ultimately came to nothing as nobody knew what Dex and Lumen were doing as the evidence was destroyed, and Quinn got off scott free in regards to the blood on his shoe. Grrr.