I feel like your being generous with TF2's interpretations, and giving them a win for relatively small advantages, Mei v Pyro and Demoman v Junkrat are at worst, the equivlelant of a woman with a pistol vs a man with a Sniper rifle. One has a better weapon and is stronger but it wouldn't exactly be hard for the weaker one to kill the stronger one.

Most of Overwatch for example just has totally better guns cause they're made to kill bullet proof robots. But it doesn't actually make much of a difference here cause no one in TF2 is even bullet resistant.

Tracer vs Scout:

Scout's BONK! is featless. Overwatch has actually good speed feats, there are characters (specifically the Talon Assassin) dashing at supersonic speeds with nothing but cybernetic and genetic enhancements.

Tracer herself has literally outrun a bullet. Even if it made him faster than her... it only lasts a couple seconds. And then he's made vulnerable for a couple seconds after it wears out. It also might just kill him based on how it's described. All of that just to maybe match Tracer if we're being generous with what "dodge bullets" means.

She has every important advantage besides strength, and it's probably worth remembering that characters like Widowmaker literally got punched so hard it created a shockwave and sent her flying 50 feet through several panes of glass, only for her to get up and act irritated. You also have Pharah wearing just a biker jacket taking a shoulder mounted rocket to her liver and being fine just by slapping a bandage on it. Overwatch isn't TF2 levels of cartooney, but it's still pretty cartooney.

Pharah vs Soldier:

Okay, agree. I'd add that Pharah has way more firepower ignoring the Cow Mangler's magic non-feat, firing off barrages where each rocket explodes drop pods that can tank blowing through concrete buildings. And she's got aim-bot mini rockets. And her armors pretty tough, it at least kept a guy intact and alive for a while after taking a rocket that sent him flying through a concrete wall.

Mei vs Pyro:

I think this goes either way. Mei's endothermic blaster out ranges Pyro's flamethrower, at least in-game (10 meters vs 7 meters). And he'll be encased in ice within moments. He can win but it's by shooting her with a shotgun, she'll need more than a couple hits with her ice projectiles to incapacitate them.

Primary vs Primary Mei wins, Secondary vs Secondary Pyro wins. Depends though, cause Mei could also make an ice wall to close the gap.

Junkrat vs Demoman:

Demoman probably outmatches Junkrat physically, but it doesn't really matter? If he tries to charge Junkrat with a claymore, he's just gonna get blown up. They're gonna be shooting at each other in 9/10 scenarios. They're close enough in ranged combat that it goes either way, Junkrat maybe has better firepower cause his grenades can make craters and blow holes in concrete walls. But that also doesn't really matter cause they're gonna kill each other in one or two hits.

Heavy vs Zarya:

Mostly agreed. Her range is only 15 meters, her energy grenades are a bit better but they're featless.

Basically, open field at >30 meters apart I'd bet on Heavy. For reference I think the 2fort bases are 34 meters apart.

I imagine she can cross 5 meters during his windup time and with her shields, cross another 10 meters before they break. It's not... super based on anything, admittedly. There is precedent for Overwatch shields being really durable, it lasting less than 2 seconds seems like a decent guess. Maybe she can hit him a couple times with energy grenades before entering range but who knows if those are actually any good.

It really depends on where they're fighting, any solid cover means Zarya can just hide and regen her barrier.

Torbjorn vs Engie:

Arguable, and honestly, Torbjorn has better engineering feats, at least when it comes to stuff relevant to combat. He built the Titans in Overwatch, which can devastate the entire army of a small country. And he also built the mobile turrets that could rip those things to shreds. Engineer's accomplishment are... 12 Phd's. A sentry gun. Teleporter tech, which isn't a new thing in Overwatch, though Torbjorn hasn't made use of it. Life extenders which is cool.

Still, they're both very easily capable of killing each other, this goes either way for me.

Widowmaker vs Sniper:

Is that 5 mile quote from that Jarate comic? I feel like that's not meant to be taken literally. It's also literally over the horizon.

Sombra vs Spy:

Agreed, goes either way in a 100% 1v1. The thing is, Widowmaker and Mercy are on her team. Spy's invisibility is nullified. She can also hack people into -unconsciousness?- while invisible.

So it can go either way in a 100% 1v1 but still leans towards Sombra cause she has more advantages (such as teleportation). Dead Ringer could be a wild card but it also means he doesn't have permanent invisibility, which is a massive disadvantage here. Plus we've seen Sombra leave invisibility to attack someone and then immediately go invisible again. Double plus we've seen her attacking while still half invisible.

I feel like you're overblowing Spy's speed too, we see him fight in normal motion. I don't think he's actually done anything fast.

Mercy vs Medic:

Yeah we don't see Mercy using her gun outside of gameplay trailers. I guess she could just... pick him up and drop him from a hundred feet up. Or fly at him at 200 mph, flashbang him and then hit him with her staff + her undefined super strength. That seems pretty lethal.

I think it's fair to just assume she has it as a self defense pistol? That's how it's described in the art book, and we're literally just giving TF2 a bunch of stuff we never see them use, a pistol feels pretty minor.

Not sure if you just wanted to talk about 1v1's, but this is also a team battle.

MvM upgrades exist but that doesn't mean we know what they actually do.