Yeah, I think 11 different results all have to happen for the Lions to miss the playoffs. Lions lose all 3, Seattle win all 4, Rams win all 3, and Minnesota loses to GB. If for simplicity you assume any one of those results is around 50/50, the odds of all 11 happening are approximately 1 in 10,000 I believe.
Even the chances of winning the division are roughly as good as being up 3-0 in a best of seven playoff series. Lions have 4 cracks at winning the division (their own 3 games plus Minnesota-Green Bay). 3 of those 4 chances are road games though.