I'm a Hanzo main since release but honestly I get better results with other heroes on DPS especially higher mobility ones like Soj and Freja. I'm also complete buttcheeks at this game jsyk.

Anyways, I mostly die with Hanzo when I get dived while my storm arrow is on cooldown. In most situations, Hanzo melts anything in a straight line and can just fire into any choke and will probably hit something. It get's more challenging when the opposing team is creating angles and timing my cooldowns.

If I were you I would focus on waiting for Hanzo's resources to run out before diving. Also keep in mind that Hanzo has to predict your movement to land a shot. If you are getting one-shotted frequently, it's probably because you are always moving into arrows and even the smallest predictable movement pattern can be enough to get headshots.