He'd love to hear what you think, and I think his points make for the basis of an interesting discussion.
I read this entire thing and I can't really think of anything else to add. It's pretty exhaustive in covering not only the problem of Hanzo but Overwatch in general. League had a similar problem where making champs and items too similar (within the roles) makes balancing too difficult. If everything is just a slight variation on each other, then there's no reason not to mathematically maximize every role. When LoL vs Dota threads crop up many people cite the unnecessary complexity of Dota heroes, but they don't realize that it's specifically this complexity, that two similar heroes who occupy the same roles (say, Dazzle and and Earth Spirit) can offer completely different team strategies, is paramount to the balance work. And when IceFrog overbuffs or overnerfs or even remakes a hero, the balance isn't thrown out of whack, because what's holding up the glass house of balance is the relative strength of team comps, of which there are countless; very rarely are individual heroes problematic. Trends and macrobalance rule Dota.
Hearthstone suffers from the same problem. Really, any game that touts the "easy to learn, hard to master" motto will be vulnerable in this area. Complexity itself is a balance tool.
So what's Blizzard to do? I'm leaning towards the utility option for Hanzo. Pushback could work. Bleed? With movement causing extra damage, like Rupture in Dota or Puncture in Path of Exile. As a Dota player I'm not opposed CC but CC is probably even more rage inducing than Hanzo's old hitbox for your average player. Ana is at risk of becoming the new Hanzo, and will only held back by her extremely high skill floor and her lack of weeb appeal.
I also agree that the pro scene, for all their mechanical competence, is underdeveloped. I would've expected that some team would, by now, be able to figure out ult timings and whatnot. I've also considered the idea that an optimal strategy might be to not damage the opposing team at all until ults are ready. The pro scene's microstrategy is pretty good (there's room for improvement of course) but the macrostrategy leaves a lot to be desired.
Also your friend touches on one of the reasons Mercy was such a problem before the Ana patch. Sometimes she could rez twice in a protracted fight, all because of the damage flying everywhere (that never kills outright) she gets to heal. I think Blizzard is aware of this but are choosing to ignore it, like they did the problem of hero stacking. They have backed themselves into a balancing corner and are delaying addressing it directly, clinging onto the notion that they can manage it with minor balance tweaks, rather than going after the more fundamental problems.
I think in between the Zen buff, the Mercy change, and Ana, we'll start to see the cracks of Blizzard's adherence to the "120 damage per second, 200 hp" baseline they use for non-tank heroes. There's a lot of damage flying around right now, and the TTK is going to be higher than it ever was before.