While it's easy to go to what didn't happen let's look at what did. We knew Dexter was saved, more or less, by Deb. And, we knew when you save someone you care. No wonder the writers needed to just go ahead and bring Dexter and Deb back together. Together they're richer as characters with plenty of tension intact.
What's more surprising is Dr. Vogel is back in full manipulating glory. This raises the creep factor with almost unimaginable possibilities. The group effort to clean up the murder scene (how to clean up an impaled mattress?) signals a new paradigm in Dexter's evolution in some kind of bizarre bonding our protagonist has never allowed. Now, this is interesting.
Clumsy as the side-stories of Masuka and Quinn are, we know they're just setups for something else so give these some space before final judgment. Same with Deb's boss.
What's big is Dexter is now empowered once more. Though, he's seemingly in a much different, . foreign, place, a pinnacle if you will, a place where he actually has a support structure of "family" as horrifically stated. Dexter has never had this, no not with Harry since the "code" was not about acceptance instead being damage control. This is the episodes "big reveal" and I'm surprised it hasn't been picked-up on as the centerpiece as it signals a dynamic quantum shift.
Other thoughts: Harry was completely absent. Battista is still marginalized, Captain Matthews has unknown dark motives as in his heyday. Quinn is back on the cusp of who knows what. Jamie's girlfriend has a secret side as, likely, so does Masuka's sudden daughter. There's plenty of undercurrent in the soup. So, maybe a necessary slow down before all hell breaks loose and in that way not a disappointing episode at all, but the calming before the explosive storm?