I also don't really buy Quinn going after Dexter so hard - hard enough to enlist help from a pretty creepy dude, etc. I bought Doakes, because they prettymuch introduced him as someone who would do that, but this seems far away from the Quinn character they were developing.
I do like not having a "super-villian" for once, but I'm starting to get tired of all the close calls. And I'm already really tired of every kill having a complication.
Maybe there's only so much they can do with the premise? They did two supervillians, they did a buddy who turned bad at the end, and they did a supervillian / quasi-buddy. And squeezed in the nutty season 2 chick and Doakes as well. What's left?
I think the only really interesting question is do Lumen and Dexter hook up (goodness, I hope not), or does she wind up on his table? Or both?
When Quinn was introduced, he was an empty vessel. I couldn't figure out what his story was or why he was there, and they've slowly been filling in the gaps, but I agree that he's been redefined a bit over time. There isn't much consistent about him. At first I was sure he was going to be the next villain, but that seems less likely now. They never really did put a fine point on his IA investigation. That just kind of stopped cold for no reason. I think it was meant to cast doubt on him personally, but they seem to be painting him now as the new Doakes which isn't really working for me. It's also weird seeing him push so hard for a relationship with Deb while at the same time pursuing Dexter so vigorously. It's like he doesn't see a disconnect there.I actually like the Lumen story line a bit (more so recently, especially after the last episode), but it reminds me of Lila but with less goth. Julia Stiles is a pretty talented actress. She's more than held her own in scenes with Michael C. Hall. We are probably seeing writers run out of ideas a bit here, but seeing Dexter help her avenge someone else's demons is an interesting twist. I have a feeling the larger story arc will be the increasing humanization of Dexter (which has happened sporadically), and this might be further evidence of that. I'm positive he and Lumen are hooking up. Seemed inevitable at the end of the last episode, but will probably happen in the next one. The image of her in the tub at least firmly planted that possibility of a Rita-replacement in peoples' heads. Rita probably ultimately failed in this series because she too dissimilar to Dexter. She became too independent and held him accountable.
Lumen at least opens the possibility of someone that Dexter can co-exist with on a more fundamental level. I have no idea if that's good story telling or not, but it's certainly something that could happen.