I'm going with coaching. There are problems on both sides of the ball, including time management and play calling. Granted, there are definitely personnel issues that are contributing to the losses, but I see that other teams are making 2nd half adjustments to us and we don't have answers.
Bottom line, this team is built around the offense and yet we can't move the ball when we need to.
Obviously, I'd agree on the 2nd half adjustments. At one time not too long ago, there wasn't anyone better than NE, now it's a major liability.
Yes, the teams built around offensive production, and yes, they've made some mistakes, gotten some bad breaks, and not executed very well in the 2nd half of games--that could go back to poor 2nd half adjustments too though.
I'd have to disagree about not being able to move the ball, unless by "when we need to" you mean in the crucial 2nd half of some away games. Then I'd agree based on horrible timing of key mistakes, some poor execution in critical situations, and overall bad luck. Otherwise, the offense may not be anywhere near 07 (once in a lifetime) standards, but are still doing pretty damn well, as they are near the top in time of possession, overall points scored, and yards accumulated per game. Anytime your offense is scoring 25+ a game, as a whole it's doing it's job, IMO---not that I don't think they share in having to execute better too.
Bottom line is that a lot of NFL teams would trade for our offensive production, but you'd have your hands full finding takers for our defense this year.