I think Dez didn't break free until a moment after the whistle. The whistle was the right call in that situation. We'd have been mad at the refs in that situation if Dez got popped from a defender flying into the pile or if the defense managed to strip the ball which is the other thing they try to do.
I think Dez played one of his better overall games today but I wish he could have squeezed that slant on 3rd and short on the first drive in OT. It also would have been nice if he won that ball that Romo threw up for him near the end zone as that would have been a huge play. It's also a shame that Romo underthrew him on that stop and go when he was about 5 yards beyond the defender. The ball was thrown late likely due to Romo's lack of faith in Dez's read/route.
It does seem as though Romo is looking to Dez a lot these days but they haven't quite got their timing down just yet. I'm really hoping that final switch is going to click and Dez can morph into a Larry Fitzgerald or Andre Johnson type of threat out there. It was good seeing Romo throw a few to him down the field again.