The more this season’s shows focus on Debra (Jennifer Carpenter), and her continuing breakdown after committing murder to protect her brother, the less satisfying and believable things get. But the more Charlotte Rampling, as a visiting police psychologist, probes the psyche of Michael C. Hall’s Dexter, the better this show becomes. So watching, for now, is a mixed bag – but it’s the final season, so who can stay away?