Favre was actually 11th and 9th in the league with respect to passing yards and TD passes. The Jets were actually 8-3, before collapsing at the end.
The Vikes won 10 games last season with Gus Ferrote and Tarvaris Jackson.
The Lions won't compete in that division, and the Bears might be better with Cutler at the helm. Then you have the Packers, who could win 9-11 games.
With that running game and no dominant team in that division, Favre really could make a super bowl run. Let's not forget that Minny's defense isn't half bad, either...
NFL is all about parity, every year there's always a few surprise teams and the Jets looked like one of them until they fell apart late in the season. Minnesota won't be surprising anyone if they win 10+ games, and the only thing they are lacking is a big play WR. The Vikings did draft Harvin, but rookies WR tend to struggle. Really if that team had a deeper WR corps, I think Favre could carry them to playoffs.
Erik