On the one hand, Dexter is the luckiest man alive. On the other hand, maybe he really is the greatest serial killer.
I think watching the show I always just looked at him as a "good" serial killer, but when you look at his achievements over the course of the series, especially this season, he's just the best at his job, his job of serial killing.
The moment he sat down next to (other) Gemini and started sucking up to him, just like his brother, I knew his plan. I did think it would take a little more work, but I guess telling him you killed his brother sort of speeds up the conversation. A little self defense, blaming the other deaths on him, brilliant. It did seem a little sloppy, hence the lucky aspect, but it adds up.
I do wonder if Praeter is the New York Ripper. If he is, then he fits Dexter's code, which is convenient for the story, but wraps things up a little too neatly. I also feel like Praeter would share that info with the group, and not just have the trophy, but maybe he's just extra careful. Maybe it's something he's saving (but everyone else knew.)
And of course Batista. I hope he lives but I just don't see how.