I figured it might be worthwhile to start a new thread on this, but apologies if people think I'm trying to be an attention mongerer.
Anyway, I think if you want to put the goaltending as it relates to wins and losses into perspective, and if you assume save percentage is the magic number (i.e. that, over time, a shot is a shot is a shot) a pretty good comparison to make is with Minnesota. The Devils and Minnesota are virtually identical in shots for per game (Minn has .4 more shots per game), and Minnesota gives up 2.4 more shots per game. (While a statistician might tell you otherwise, it seems to me that the shots against differential is only slightly statistically significant, so that's the assumption I'm going on). Minnesota and NJ's goals for and goals against are also pretty close. (NJ has 163 GF/Minn 154, NJ has 160 goals against and Minn has 155 goals against, and Minn. has one game at hand).
Now, if you look at Minnesota's goalie splits, it lines up pretty well with what even the biggest Marty haters would realistically want to see, Schneider getting about 70% of the starts. For Minnesota, together, Kuemper and Harding have gotten 49 starts, and Backstrom has 21 starts (Bryz has only one start so I'll leave him out). Recognizing that it's not a precise calculation, if you put their save percentage together, Kuemper and Harding have a save percentage of around .925. Backstrom's save percentage is virtually identical to Marty's (.899 to .901, respectively). One place where the comparison seems to break down on its own terms is that Backstrom seems to have faced more shots per game than Marty, since Backstrom's GAA is about .5 higher than Marty's. So in other words, and again, assuming save percentage is at least a very revealing statistic, Kuemper and Harding are almost the same as what we would expect Schneider's save percentage to be (although it has taken a dip by virtue of his last two starts) and Backstrom is very close to being the same goalie that Marty is.
Minnesota has six more points than the Devils, with one game at hand, but has also seven shootout wins to the Devils zero.
I recognize two flaws in addition to the assumptions noted above. First, the goal support factor for Marty and Schneider. While for our purposes, I'll concede that it's random, I think people underestimate the effect of Marty's puck handling abilities, which definitely showed last night, and which Kowalsky -- Albany coach -- in an interview has said can impact the game more than you think. The other flaw, perhaps, is that the sample size is not sufficient.
So recognizing at least those flaws, one could say that Marty has cost the Devils a few points as compared to a situation where Schneider was the number 1 goalie from the start of the season. For a team that will be scratching and clawing to get its way into the playoffs, it matters. But until the Devils can manage to score more goals (which we're starting to see now, but we'll see how long it lasts), we can't expect the Devils to be much more than a low seeded playoff team, even with an ideal goaltending situation.