So maybe the problem is that got too much MMO/MOBA logic, in what is really more of a TF2 successor in the Class Based Shooter genre.
Developed by a team that mostly comes from developing WoW, and had originally intended Overwatch to be an MMO called Titan.
That they never got designing “Heavies” right, because they were too focused on MMO mechanics.
And that perhaps the way forward is designing Tanks to be more like “Heavies”.