Dexter was awesome for many seasons. The season with Trinity (Lythgoe) was probably the best.
But then the blonde killer girlfriends started. The first one couldn’t act at all, and then the show unraveled. I know they stuck to the book with the sister finding out, but on tv that ruined the show. Her morality played an important part in allowing the audience to sit and enjoy the show. The ghost dad started losing it. And of course the series ending. THE ONLY THING WORSE WOULD HAVE BEEN TO HAVE THE LAST EPISODE TO BE AN IMAGE OF STATIC OR POSSIBLY THE FILM REEL CATCHING FIRE ON SCREEN. Worst series ending ever.
No, You are wrong about her acting ability. The actress playing Dexter's wife was perfect in her role as a damaged, beaten wife. I've met many of them in the Food Bank i founded. She was nominated for a couple of Emmy awards. She earned them for her portrayal.
Deb's emotional unraveling is also exactly spot on with the moral dilemma she was forced into.
As for what you refer to as the "ghost Dad." There was no "Ghost." That was Dexter's own constructed memory of Harry guiding him through his life of killing the "right" victims, his artificial conscience, reminding him to keep to the "Code of Harry." It is important to the story arch and Harry's fewer and fewer appearances over the story are evocative of his dissociating with that guidance and code Harry instilled in him as he lets go of Harry's rules as circumstances box him in.
As for the ending? Do really think that psychopaths kill themselves out of remorse? Not on your life. Dexter's life, the entire essence of his being, was ALWAYS about re-direction. It was a perfect ending, demonstrating that he AGAIN re-directed everyone and pulled off the ultimate magic trick, his own disappearance, faking his own death.