Vision on a DE is useful for 3 things:
1. For defending against the run so that you don't get faked out as easily by the back and you don't do stupid things like in the replay given.
2. For jumping the snap. It has been confirmed by Bort that there is a vision check to see if a DE is able to jump the snap.
3. For certain types of pass rushing. If your DE just tries to go around the edge every play, then vision is not as nessesary. However, to have a good inside rushing move, then good vision is very important so that the DE is able to quickly see the inside gap in the offensive line.
As the agent of three OTs though, please keep ignoring vision guys
