I've never even played flag football.  But my understanding, after reading some excellent writers opine on the subject, is that the Seahawks' Defense is indeed that simple and predictable.  And its excellence is made possible by the Big Five (Thomas, Chancellor, Sherman, Wagner and Wright).  Each of them does his job so well that everyone else on the team can narrow his focus and dominate his contests.

Remember Byron Maxwell, who got four interceptions in 2013 in only 5 starts?  Those interceptions were a direct result of QB's not wanting to throw to Sherman, and since everyone on the field knew the QB was loathe to throw Sherman's way, Maxwell 'only' had to stay on his assignment's hip and keep his eyes on the QB.  Do that, and he can ball hawk all day long--which he did.  The league adjusted to him in 2014 when he was a full-time starter, but his success came from everyone else locking down their parts of the field and letting him attack, attack, attack on the balls of his feet.

My understanding on Chancellor is that Strong Safeties tend to break down a few years earlier than Free Safeties, so he's got that working against him.  But I've also seen studies of top-tier SS that show they don't really stop being above average until their early thirties.  The worry with Chancellor (as I understand it) has always been that his style of play is so extremely physical that, like a bellcow RB, one day he'll turn into a pumpkin and that'll be that.

One thing on the D-line that I don't think gets enough mention.  Brandon Mebane was not the best DT in the game--he wasn't even top 10.  But he was, essentially, a Nose Tackle for a 3-4 system, which meant he was big, immovable, and could reliably close off even against double teams by interior linemen in the run game.  The downside was that he had close to zero pass rushing ability (thus the immortal gif of his belly roll after he recorded a sack).  Richardson grades extremely well in the run game (he was #5 among DT's last year or the year before, I forget which), but he's not a Nose Tackle like Mebane was (and even though Mebane was in Seattle's quasi-4-3 scheme, they basically played him like he was a 3-4 NT).  I don't know what effect that will have on the run defense, but it's going to make a difference somehow.  I'm just not educated enough to predict what that impact will look like.

Thank you for the kind words. As I was reading your response about your thought processes and defense, a light bulb went off for me as well. When it comes to offense/defense on passing plays, for the down lineman the roles are flipped. 

Traditionally, one thinks of defense as being where your opponent is coming at you, and you react to what he is doing. A cornerback reacts to the receiver's moves, a shortstop reacts to where the ball is hit, a point guard reacts to what his opposite number does while bringing the ball up the court. On a chessboard, it's 0-0 or 0-0-0. In football, on a running play that still holds true. The offensive line comes off the ball trying to push the defenders back in order to gain territory. But on a passing play, the defensive line is playing offense, trying to breach the castle wall and sack the town. (Side note: in interviews, Deacon Jones, who is credited with coining the term "sack", stated that's what he was thinking about when he first used the term to mean taking down the QB) 

If I've learned anything at all about Aikido while reading SSI, that's exactly what happens between offensive and defensive lineman on a passing play. Take the force coming at him and redirecting it away from the aggressor's intended target. Making the aggressor use up energy and tire himself out. For those of us here who are in a certain age range, we well remember "rope-a-dope". Ali let Foreman throw all the haymakers and use up his energy reserves; just protecting himself and biding his time. Anyone who was watching the first three rounds thought this could be a short fight - all Foreman needed to do was actually land a couple of those thundering right hands and that would be it. But Ali weathered the storm, then launched a fast-paced offense at a tired opponent who no longer had the stamina to hold up to the pace.

On the defensive line, while you have (in Seattle's case) four men who are ostensibly a unit, much of defensive line play can come down to one person winning his matchup and breaching the wall. If he gets tired another man can be substituted without a great deal of dropoff, provided you have sufficient skilled depth. So you have defensive coaches wanting to make sure their guys are fresh and going full-bore all the time. That does not apply on the offensive line. The offensive line is much more reliant on teamwork and continuity to ensure no breaches occur; you pretty much never, ever see the O-line guys get a breather. If they come off the field it's with medical personnel walking right next to them.