I agree the latest episode was the worst of season so far but I have enjoyed this season so far, more so for the Dex and Deb stuff, which I like. Last season it had gone off the ball, they needed to do something different with the characters and I like it.
Dexter has always gotten slightly more careless as he has gone on through the seasons, its an ongoing thing so I have no problem with him slipping up again. Its a sign of how much everything else is getting to him.
I'm only on phone so I'm going into great detail but I pretty much disagree with you. I think this has been best season since 4, but yes the last episode wasn't quite up to scratch