I have to wonder why they kept the horse collar tackle legal if it by the jersey. The whole point was to prevent injuries and a horse collar tackle by the jersey is just as prone to injure a player as one inside the collar.
I agree with cutting Willams some slack since at strong safety, he is usually not responsible for primary coverage on deep routes. It is he responsibly to help the DB though, and on a some deep routes he has come up short.
Anyway, TRRW is much more effective if he can play in mostly run support. In college, he basically created his own position, which Coach Stoops called the Roybacker. Basically he was a safety/linebacker hybrid. Dallas has been playing him more in pass coverage, and so he is out of position.