Dilfer is talking football 101 here. The defect isn't in the players, it is in the base cover 3 scheme. Every scheme has weaknesses, and he is describing the weakness of cover 3 press.
The assumption is that a single high safety can't cover 2 guys if they cross. The other assumption is that a technically sound press bail cover 3 corner leaves a vulnerable area on the left or right side of the field when he turns to bail to the deep third.
Both are technically true, but Seattle gave up damn near nothing down the deep middle this year. And Sherm has proven to be able to watch a QB when he turns to bail, and has broken up a number of back shoulder attempt on the right side. Dilfer is spot on in saying Maxwell gets picked on in that left area, SF, Denver, and Nola all exploited it to their advantage.
HOWEVER, Seattle has changed it up just enough to work to some big plays. The Kam pick vs Kaepernick was us knowing they wanted to take advantage of that spot ans sliding Chancellor's zone over to the left to take it away. They showed a tendency, we figured it out, and patched it. Later, they got a completion over Thurmond doing the exact same zone Kam had done, the play worked for SF, but it was still a dangerous pass.
What Dilfer left out is the biggest vulnerability of the Hawks, one that the Colts exploited about 3 times. Catch Seattle in cover 3 press, then send 4 go routes. Simple, but it takes a strong armed guy to do it. Last year, Sherm sealed the home win over the Rams when they tried it, but their QB doesn't have much arm and couldn't get it to one of the two guys Sherm was forced to split his coverage on. 4 go routes doesn't take the time that 2 deep crossers does, so it's a lot less dangerous for a QB's health to call 4 go.
Part of the reason I knew we would beat Denver was that Manning simply doesn't have enough arm to take advantage of those areas of the field. There are really many teams with the combination of strong accurate QB, fearless playcaller, and speedy WR/TE combos to take advantage of our defense with 4 go.