Here's a table that shows the main five non-Niedermayer defensemen, and their even-strength performance before and after Scott's December debut:
(click on image to enlarge)
For Pronger and O'Donnell, I think the improvement mostly stems from the sharing of tough minutes, no longer being the only shutdown option on the blueline. Really Scott's return enabled the team structure to go back to what worked so well for them in their 2007 cup run: a Norris defenseman covering most of the critical minutes, while a third pairing cleaned up on easy minutes.
It's a bit odd that Schneider and Huskins saw their outscoring productivity drop post-Niedermayer, but it wasn't a huge difference, and with Huskins in particular it could be attributed to additional even-strength minutes, freeing the superstar d-men to also manage the special teams minutes. While their numbers are very solid, it's important to remember that this system used to work with Huskins and Dipenta, who is roughly $5M cheaper than Schneidermayer.
I did want to focus a bit on Francois Beauchemin's play, however, who has spent nearly his entire career letting Scott cover his ass. You can see that Frenchie in particular struggled without Scott (and was redeemed upon Scott's return), and I think a lot of that stems from the bad habits that developed under Scott's tutelage. I've drawn a little schematic to the right to demonstrate this.
Normally, when a puck gets dumped behind two defensemen, it's likely a 50-50 split which defenseman will go retrieve the puck, depending on what side of the net the puck is directed. For Scott and Frenchie, though, they've developed something like a 80-20 split, where Beauchemin gets only the very close dump-ins and expects his fleet-footed partner to gather the rest. I remember watching a Scott-less Beauchemin very carefully in the opening 34 games, and to my eyes I could spot this happening to poor spoiled Frenchie -- he was so used to not retrieving pucks that he'd often leave his defensive partner with silly responsibilities that only a guy like Niedermayer could make look effortless.
I'm not blaming Beauchemin for anything, really -- if my back was always covered I'm sure I'd develop bad habits also, but that's another reason I really want Scott to return; he not only helps other defensive pairs manage their minutes better but also carries bad-habit Beauchemin into respectable results. Someday Frenchie is going to have to re-learn his puck responsibilities when paired with an average partner, but I don't want it to happen this year.
So that's a bit more on Scott's roster impact, at least at even strength. I'll close with a lame analogy, mainly designed to incorporate a crazy e-mail image that my dad forwarded to me. Scott's so valuable on the ice that putting him at the top of a lineup makes an ugly dude like Albert Einstein look like a beautiful blonde like Marilyn Monroe:
Step away from your screen to see some crazy-ass magic eye effect.
Insanity. Go Ducks.