Unless you have Aaron Rogers at QB, see post above, the chances of hitting on a hail mary are very, very slim in the NFL. I cant even remember the last time a team won a game off a hail mary in the NFL that was not the Pack. They seem to win a game like that every 1-2 years.
The highest percentage play for Dallas to have run would have been to lateral the ball back and forth and hope the defense overplays to one side and you can get a free runner down the sideline, just like Miami did against the Pats last season.