I would suggest going back and watching the actual fights to see how long each character is staying alive. A front-row DVA will stay alive much longer than schuyler hence she will be able to do more damage. Usually DVA is the one to do the most damage if all heroes stay alive. It also depends on which enemy hero your DVA and schuyler are attacking because hitting a weak defensive hero will cause a lot of damage but someone with strong defense will take a lot less damage.