I agree with most of the article. Couple other thoughts why I think the show is sliding:
(a) The walkers are no longer a viable threat. Most of the group just approaches them casually to dispatch them. While I do think the angle that the remaining humans in the world are the greater danger than the walkers is interesting, it is boring to watch most of the walker battles. Sunday was a good example. Tara was completely overwhelmed, but was able to push the walkers down while killing a few.
(b) Just a crap load of negativity. Most survivors just have a crap attitude anymore. As refreshing as it was watching some positive attitude and joking from Tara, by the end of the episode, she was just like all the others, sitting in a slump over the loss of Denise. Not that it wasn't legitimate for her, but everyone is ending up in the same emotional state.