There could be a lot of logical reshuffling of divisions if the NFL really wanted to.
Just a quick and drastic restructure without much thought:
AFC North: Buffalo, Cleveland, Pittsburgh, Baltimore
AFC East: New England, New York, Miami, Jacksonville
AFC West: Kansas City, Denver, Arizona, Houston
AFC South: St. Louis, Cininnati, Indianapolis, Tampa Bay
NFC North: Minnesota, Green Bay, Detroit, Chicago
NFC East: New York, Washington, Philadelphia, Dallas
NFC West: Seattle, San Francisco, Oakland, San Diego
NFC South: Atlanta, New Orleans, Carolina, Tennessee