No, he's an original character for the TV show that is supposed to be an amalgamation of several characters from the comic according to a story I read on Entertainment Weekly or Zap2It.Is Garieth from Terminus apart of the Hunters storyline in the comics?
As for this episode...the stuff with Daryl's crew running into Rick and them was awesome. The flashbacks were stupid and took up precious time that would have been better served on current events. The Terminus stuff was OK but a cliffhanger exposing the sinister secret of Terminus would have been better than Rick talking tough while locked in a train car.
This episode just reiterated the absolutely terrible pacing this show has. This ep didn't even feel like a season finale but rather another regular episode because the show is paced so badly.