Changed my mind back, putting Dexter and Lumen together romantically was a bad idea, at least with the direction they chose to take it. Their whole shtick this episode basically devolved down to how much they lurrrrve each other (including Deb coming up with a wild theory about vigilante couples which is true only by the virtue of unsubtle writing). On top of not being very interesting to watch, it just telegraphed how much Lumen wouldn't be back next year. Or if she is, it'll be in a very limited capacity.
I hope it's at the least just a case of being a setup episode for a fantastic season finale but this still wasn't an ep up to the standard of the last few IMO.