One thing that all these QB's had in common is the all had good running backs and offensive lines
The Seahawks were 24th in the league in 2011 in 3rd down conversion %. This year, 12th place. That wasn't because of Marshawn Magic, or the OL, or Sydney Rice dominating. That was all about wise decision-making from the QB position. Finding the open man and not panicking all the time and taking terrible coverage sacks like Tarvaris used to do. If not for those couple crap-fest losses in the first quarter of the season, that number would look even better.
Same thing with our run game: Seahawks were 21st in the league in rushing last year. 2012, with almost the same personnel (Okung, Unger, Marshawn, Leon, Mikerob, Breno, Moffit, etc), 3rd in the league. We didn't add any high-profile signings, just a couple mid-late round picks.
Back-up RB Turbin didn't make us go up 18 spots. CLEARLY that was all about Russell Wilson coming in and making us that much more dynamic, and making defenses stay honest. Having "good running backs" is about more than just fantasy stats, and breaking a bunch of long ass TD runs but getting stuffed most of the time (Jamaal Charles, MJD, CJ2k) - it's about those intermediate runs of 5-15 yards that defenses give up when they can't cheat with 8 in the box and/or get caught over-pursuing.
/rant
Seriously though, these guys are the future. Defenses can't simply adjust overnight, or over one offseason, with studying and game-planning alone: they'll need to get quicker, stronger, longer-limbed, more agile defenders, and that's going to take time to build up. The thing that makes a team like Seattle so scary is that our defense is already built to stop the read-option...other defenses are going to take years to catch up.