Part of the problem IMO with the long term sustainability of this show is I'm starting to get the 'rinse repeat,' sense on the plots. People will start to get bored if there isn't more of a mission for the group to complete.
Thank the episodic nature of the source, even if the TV series is not adapting every plot panel by panel.
Daryl has to learn the hard way about what makes a family; Glenn telling him that the group
is family should have meant something to him--along with the fact that extreme personalities (Merle, Shane, the two jail punks) have never worked out well.
Patterns count, and Merle follows a form of it that will only lead to more tragedy for Daryl, and likely cut a permanent rift between the group and himself.
Rick's loony syndrome/guilt must end soon; it was explored enough with his "Rick the Barbarian" initial reaction, and the imagined phone call, so it just seems like a cheap way to have his guard down when enemies come calling.