You've taken me down a rabbit hole now. I did the math. Over that time period, if everything were random, you'd expect to see 3 WCs come from a single division about 1.1 times. It actually happened 3 times. Well, not all things are equal. Divisions play sets of games against a single division in the other conference and one in their own conference. Teams that get lucky enough to play weak divisions in those games have a substantial advantage. So 3 times in 12 years seems a little high, but not too bad.
Now, though, with 4 divisions and only 4 teams per division, the math is different.. The odds of it happening in any given conference in any given year are less than half what they were before. That works out to a likelihood of it happening once every 27 years. Again, that assumes all things are equal, and they aren't. The same schedule effects are in place, but also, for instance, we know that the NFC West teams are all pretty strong, relatively speaking, so they have a much better chance than a random collection of teams would. But I won't be holding my breath.
And yeah, an entire division can go 14-3 now. I'll go out on a limb and say they'd all make the playoffs.
