I tested my win threshold stat out on the recent Stanley Cup Finalists, to see which teams seemed to rely the most and the least on goaltending (numbers are adjusted for scoring level):
1998 Detroit .883, Washington .906
1999 Dallas .879, Buffalo .915
2000 New Jersey .884, Dallas .906
2001 Colorado .874, New Jersey .860
2002 Detroit .883, Carolina .901
2003 New Jersey .886, Anaheim .913
2004 Tampa Bay .877, Calgary .900
2006 Carolina .892, Edmonton .887
2007 Anaheim .889, Ottawa .887
2008 Detroit .867, Pittsburgh .903
2009 Pittsburgh .895, Detroit .871
Not surprisingly, all of the recent Stanley Cup Champions have low win thresholds. They would all have been good teams even with subpar goaltending. That doesn't mean they would have won the Cup anyway with a mediocre goalie. In that case most of them likely would not have won, although one could probably make an argument for the two teams that employed Chris Osgood. The average team from 1997-98 to 2008-09 had a win threshold of .904. The average Cup champs had a win threshold of .883. Clearly, winning the Cup is a team effort.
Most of the Cup finalists also have good numbers, including some of the surprise Finalists. Only two of the teams had a number that was well above average. Those two were the two teams that relied the most on goaltending to get where they ended up, the 1999 Buffalo Sabres and the 2003 Anaheim Mighty Ducks.
This suggests that teams that strongly outplay the opposition are generally better Cup candidates than teams that have top goalies but do not excel at scoring or shot prevention. We can look at teams like Chicago and Washington and wonder about their goaltending, but that is the type of team that has won the Cup recently while teams like Vancouver and New Jersey have not. Percentages can play a big role in a short playoff series, but on the other hand a goalie can only do so much. At some point his teammates will have to pick up some of the slack if they want to end up winning a championship.