I don't think everyone has become a ruthless killer. Glenn wanting to open up that other train car during their escape from Terminus showed he has some of his humanity intact. Michonne has demonstrated anything lately to suggest she's gone off the rails either. Daryl also saved Noah, but when around Rick he tends to follow his lead. He was ready in Season 3 to give over Michonne to the Governor.

One thing I've liked about the show, particularly during the early seasons is that it's brought up some interesting moral debates about choices the characters must make and where they draw the line in terms of survival and humanity.

 

Perhaps it would've been more compelling overall if Beth had been captured by Gareth's group, and Rick/Carl/Michonne/Daryl had teamed up with Carol to get the others out. That would've added a couple of episodes onto the front end of the season and enabled them to still have the Hunters resolution at the church. The brutality of Rick and the group's attack on Gareth would've been a powerful conclusion for the midseason finale.

The only thing I like about the hospital arc was that they returned to Atlanta. But that could've been done as part of a medical supply run, and they could've just run into Dawn and Co. as they did with the Vatos.