This is absolutely incorrect.
If Roadhog tries that, he dies. FAST. Winston's shield won't last long enough for him to do so, either. D.va can manage it for a few seconds with Defensive Matrix, but that's it. And Zarya? Zarya's strength revolves around her bubbles, which REQUIRES that she only be targeted for a few seconds every cooldown, and can block the same for a single other hero.
You're describing Reinhardt, not tank heroes.