my thoughts
i think it was written if there was no season 6, since this was supposedly the last one. They could have easily made a bunch of scenarios happen that would head into season 6, but It was a happy ending: quinn and deb together, angel and NY undercover girl, masouka and his big boobie date, dex gets his kids, etc.
It didn't top season 4's ending, but i don't think anything will =) I thought lumen was gonna die, just cuz Dexter is a really unlucky guy. Of course, he's not gonna abandon his dark passenger just for her, so yeah, this wasn't gonna work if she stayed.
Overall, it wasn't the best. there was a lot of plot holes, and a lot of dumb stuff happening. The LA police force continues to be the dumbest force in the World, until Deb actually started getting things right during the end of the season. It's so... i dunno, Dexter can totally manipulate his whole team whenever he wants. i find that unbelievable.
Also, they just dropped the santa muerte murders like it didn't happen. didn't one of the brothers escape?
Julia Stiles... i like her, but... not exactly the best guest appearance. she seemed to be dragging Dexter down, and it became more of the Lumen show, with Dexter helping her out.
The Stan Liddy dude was good. He brought excitement to the show. That Jonny Lee Miller guy (first time i've seen him) was awesome too.
i would rank it one of the lower seasons overall, right beside season 3, but their worst is still better than almost everyone's best.