If this sounds completely out of context I'm on mobile so I can't see what you replied to but I'm gonna assume it was me saying Tracer can predict Hanzo's shots.

Tracer isn't doing it based on reaction, because the projectile moves faster than humans can react. In which case you give her enough time and space to get a free clip, which by itself can kill you, and get halfway through her reload before you can fire at full charge again. She blinks through you after that, she gets another clip into you, if you're still alive you're a lucky man. McCree is a much better counter since he can vary up his shots and stun her into an easy one shot. Melee actually works against her in this case since every time you do it she is forced to blink.