Season 8 has not been a very strong season, it's on par with season 6 and the slowest and weakest of the whole series. Throughout season 8 there has never been a sense of closure for one of the most loved TV series of all time, and this episode follows.
If this episode was the finale of a normal season, and not the entire show, it would be fantastic, possibly one of the best. However this episode does not do a good job and closing the stories of the characters that we have grown to love over the past 8 years. You only see some of the main characters once in this episode, and they barely have any lines to say, and suddenly that's it. WHAT!? This is dreadful storytelling, and lazy writing. The creators of this show should have realised the size of this show's fan-base, and decided on ending it on a high note, much like Breaking Bad did, with that show's outstanding ending.
However this is not an entirely bad episode, like I said. The scenes with Dexter and Deborah are fantastic. There is a strong emotion there, and their scene in the hospital is one of the best scenes in the entire show. It's just a shame it is all wasted on an anticlimactic ending.
The second half of season 8 should have been Dexter on the run, and eventually abandon his family in order to protect them, eventually leading to how this episode ended. But instead they gave us 12 episodes of nothing.
Dexter is truly one of the greatest TV shows of all time, but also has one of the worst finales of all time. I am not giving this a very low rating, because this is still a good episode itself, just not a good finale.