He also happens to have some of the loudest footsteps in the game with his spurs, so you should often be able to hear him coming if he's trying to flank.
Just noting that this is a really nice detail. Blizzard has always been aces when it comes to sound design and understanding how it plays into the game experience. I had no idea that footstep sound was actually part of the balance, but it makes total sense.
And Hanzo's special is just dumb. It's easy to see coming and easy to avoid.
Almost every large AoE ultimate is easy to see coming and avoid. You're not supposed to use them to get kills, you're supposed to use them to occupy space.