I feel like everything you’ve said stands on one thing: that you follow the game’s classification of hanzo as a sniper. He really isn’t.
It’s akin to saying symm is a support and thus she’s underpowered because she cannot heal. (She is underpowered but it isn’t because she can’t heal)
Likewise, if we’re going to view hanzo through that lens then yes he will be overpowered. A character with one shot ability that is also mobile. But the fact is he trades long range consistency for mobility and higher dps.
Actually grappling hook isn’t even that bad either, it’s got a longer cooldown than lunge but has some very creative uses to slingshot widow.