I think the lack of a regular offseason hurt the Jets this year. As someone already mentioned the "island of misfit toys" strategy of team building is the type the Jets personnel dept. employs. This steady stream of bringing in guys from different teams with different philosophies would likely require offseason training programs, passing camps, mini camps, time spent together training in the weight room, etc. to build that single-minded team chemistry that the Jets displayed in 2009 and 2010.
That was missing this year, and the team lost some quality locker room veterans to free agency and retirement (e.g. Cotchery and Woody to name a few) and their replacements were either less effective or not as clutch in key moments and disappeared for stretches of the game (Wayne Hunter and Plax).