People keep posting this gif as if it is 100% undeniable. Put a player with good enough muscle memory can pull that degree of aim off. And we're talking about pro level here who runs with a high sensitivity to boot. Also, youtube plays vids at what, 30 fps? And taimou probably runs the game at greater than 120 fps.
I'm not saying the video isn't sketchy, but I wouldn't call it proof of hacks. Watching it in slow motion you can see that his aim going from lucio to D.VA (? at first in low res I thought it was someone else) across the bridge is not a straight light and curves upward like natural human movement would.
https://www.youtube.com/watch?v=Y1d04Q4XO30
That's just my perspective after watching that video a bunch of times. It's easy to just look at it once and conclude that is hacking cause people don't know what a pro level player is capable of. Even player to player is different and taimou plays at a much higher sensitivity than most pro players (to my knowledge) do.
edit:
Oh right, I forgot to address the fact that people think D.VA was off screen. She was on screen several times when he was unscoping though. I think benefit of the doubt is in order for the player. I don't consider that to be a major issue. I mean, certainly if someone is going to be banned you need better evidence then this imho.
Could be a result of different graphics levels. The artists sometimes have missed low res fixtures allowing small advantages for playing at low graphics settings. They fix these as they spot them though or as they are reported to them.