From Deadlines article
Darabont, who spent five years trying to get a TV version of the zombie saga off the ground and wrote and directed the AMC pilot, hails from the feature world, and I hear that he never quite adjusted to the daily grind of producing a TV series. Last December, he considered forgoing a writing staff for Season 2 and assigning scripts to freelancers but ultimately went for the traditional writing staff model recommended by the network and tapped Glen Mazzara as an executive producer and his No. 2. It is unclear if The Shield alum Mazzara, who has showrunning experience, would now step in to run Walking Dead. I hear that the behind-the-scenes turmoil has not affected production on the show, which continues as scheduled.
So this may be just him stepping back from something he knew he would only hurt. May be for the best. Like you said though, the last thing we need is a series meandering about chanting "Plot...Plot...Plot..."