It doesn't work like that anymore. I can agree to an extent about extended hitboxes, but they've LONG since removed the around the corner headshot.. even then, it barely ever existed and/or could be abused, it was just something in the game that -could- happen. I mean, if it was getting abused, then you're fucking awful for trying to sit behind a corner like that, wtf were you thinking? I dont think there is really ever a moment i'm standing still. If you walk out into a headshot sure, that sucks, even in my clip above I hit lucio trying to come around the corner w/ a sonic arrow; random, I even said it in game like holy fuck random.
It still takes him 1.2 seconds to get a full charge, which does 125 damage. 250 headshot. He can only send -oneshotters- every 1.2 seconds in an area; people neglect the idea of treating it similar to widow's that appear by avoiding sight lines. You can easily time against him.
Even then -cancerous arrow spam- If you're not doing it w/ every character, you're dps'ing wrong. Sure you won't get the 1 tap w/ mccree, 76, or anyone else but it definitely puts in work and i've managed to body many of people doing that w/o hanzo. Pre-fire helix into burst gg. I couldn't tell you how many poor zenyattas have been at the end of that. Even JR and Pharah are amongst the more spammier champions.
Regardless, fixing/doing anything to Hanzo is so low priority. Only the smallest spectrum of autist are complaining about it. More prominent issues like Road hook, and I'm going to go on the assumption that they're gonna try to figure out about this 3/2/1 76 spam, but that, I don't know. New Symm could potentially fix that? prob not.