GWill has really struggled lately on the defensive end. Still makes good rotations but has been getting torched by smaller players. Brad might be asking too much of him to try to guard them out on the perimeter.
Unfortunately, there are no good answers for the modern pick and roll. The Celtics choose to switch on picks, and it leaves G Williams on guys like Paul more often than we'd like. The alternative is to let the guard try to stay with their ball-handler around the screen, which is a losing proposition against a good shooter.
IMHO they should look at the rules on that particular action. It's a bit too easy for the offense and a bit too impossible for the defense. If nothing else, get back to calling moving screens.