A team really that uses Roy Williams wisely can get a bargain out of him. Teams should look to how Michael Lewis was used by the 49ers. Lewis was another "in-the-box" safety who was written off in Philly bc of his liability in coverage, but he has been a productive player for the 49ers and an impact player against the run game. You hardly see Lewis get lit up or burned in coverage bc they really limit his responsibilities. Teams like the Niners or Pats a few years ago who use a lot of cover 3 can always use a traditional SS.
A 34 team really benefits from a strong safety who can help in run support and can cover the flats. This is why Harrison was so big in the Pats scheme, the 3-4 is very vulnerable in the near perimeter, the flats. Outside swing routes and screens present mismatches for OLBS.
Best way to run at a 3-4 is right up the gut, through one of the A gaps (if the team does not have a dominant NT, which most teams don't). Generally the OLB's are taken out of the play by that approach, the SS has to get the ball carrier as the interior linemen often get matched up against one of the ILB.
Ofcourse, if a team goes 5-WR formation you are probably going to pull your in-the-box guy, just like you are probably subbing your big NT for a guy who can offer more in terms of passrush. With the way offenses are attacking defenses now, alot of traditional positional players (run stuffing mike, in-the-box saftey, big NT) have become situational players.
Also, I just want to throw this question out there... Has Roy Williams really regressed so much as a player, or is it simply that the game is now attacking him (and players like him) differently with the proliferation of wide-open offenses? I think Roy Williams in another era of power-run football could have been a effective player instead of the goat.