Also, why does he lose to Wonder Woman and Killer Frost? Do we realize that DS space control is at a point where you have to move in between low shots, down 2 and forward 3? In a game where most have to dash in or jump to start offense, this is a great couple of tools to have, and Wonder Woman, Superman, and all these chars that must honestly dash/air dash in HAVE to get around it, and it's not as simple as it appears on paper.
I don't even know if it's obvious that he loses to The Flash. Flash has to approach honestly and I'm not sold that it is as cut and dry as punishing low shots = victory. Deathstroke's gameplay has gone so un-evolved since the patch that I would wager very few are actually looking at his tools properly in all the ways they should (Down 2 would be the obvious one: its buff has done so much to change his anti air and footsie game and yet except for a few people are not looking at it in the right light)