As I'm sure others have stated its a combination of pretty much all of the above but for me the pass-rush option is on the bottom of the list of reasons.
I think many here are perhaps confusing lack of pass-rush as in lack of pass-rush completions for sacks. Also, for some reason as always refs are turning a blind eye on offensive holding on our guys. And I think the Seahawks are blitzing more to counter that.
We've also faced some really great QBs + Offenses in all 4 games.
And despite the numbers, I think we've done quite well against Rodgers, Manning, and Cousins.
Rivers was the only one to beat us with amazing plays, gutsy MVP ball.
Rodgers more or less was man-handled and raked up yardage in garbage time.
Manning was stifled until that last minute in which he basically exploited Josh Thomas' zones when Burley went down after getting tattooed by Kam.
Cousins was awesome on a few of his throws to D-Jack but if you give the Seahawks any one of the Ints that dropped out of Thomas' and Wagner's hands his 102 passer rating plummets to 78.
I actually think the Seahawks are also playing it smart in that they've been adjusting, adapting, adhering to the rules emphasis... and its quite obvious that it has taken them out of their element as a ball-hawk defense but they are playing within the rules and once they get more acclimated to that style and understanding more what they can and can't do, they'll play more loosely and start ball-hawkin it up.
And also I think Quinn is also close to figuring out the best pass-rush groupings paired to certain situations, it helps that everyone is healthy, and the younger guys are getting needed experience, it took until the Cards game in 2013 for the D-Line to really hit its stride. And I feel they are close to being dominantly consistent.
It will all come together, Seahawks are 3-1 against some pretty good teams. Even the Redskins have a decent team, RG3 lost that game in Houston with inept RZ play, they took the Eagles to the wire, and had one really bad game against the Giants. But they have a solid D with a great pass-rush plus a balanced offense with big play ability in Desean Jackson. If they can get healthy, they'll start to roll some momentum their way in games.
Not worried about the Seahawks at all. A lot of people said that this team can't win without our defense and getting lucky with key turnovers in key moments.
3-1 says otherwise.