I have a bad feeling that the writers have decided to set-up the eventual happy ending of the series by "taming" Dexter into someone who can ride off into the sunset after losing the duality of his character, that he was someone equally capable of killing an innocent as a guilty person, and prevented from doing so only by the ever-sketchy control imposed by The Code. Remember that Dexter? Seems like a million years ago.
I was hoping Rita's murder would propel Dexter into an even more precarious state. If he were getting less and less in control, and Lumen were far more dangerous and vengeful, this season would be a lot more dynamic. But then the writers would face the problem of how to pull off any kind of happy ending for the series (which I kinda do want to see).