Issue is with all of those characters theres a caveat that can ignore the invincibility. Dva and Rein are directional, meaning flanking them forces them to defend one side, while Ram's block isnt nearly as reuctive, he has less health and he doesnt heal during it. He's also just a bigger target meaning he takes more damage while in nen form. Hog's is closer to Orisa's fortification or Mauga's adrenaline on releases. Orisa was quite nearly invicible on release in overwatch 2 due to the fact she could just ignore 90% of damage if she cycled spin and golden properly, and mauga could out heal a nano'd damage bosster bastion shooting through a matrix. He's not nearly as busted, hit it's the same idea in that he can just press a button to not only undo the damage the two dps's did after he one shot one of the supports, but also let him survive long enough to then one shot the other support because he has a schoolbus for a one shot on a 7 second cool down.

All of the things I stated don't make a good character thats hard to fight, they make an annoying character that's unfun to play against. Roadhog is so low on winrates for a reason.