Do a reverse of combining offense/defense dps. Split main tank and off tanks. They are far more difference between them than offense/defense dps.
When you queue as main tank you can choose between orisa/rein/sigma/winston
Off tanks you get d.va/rodhog/zarya/ball
Orisa and Sigma can be buffed so tanks will stop whining. Also prevent dps whining about double shield.
Off tank mains will no longer be able to act like they are doing people a favor by queuing as tank and then play off tank. Supports too. Meaning we will all be at the mercy of a main tank, just like how most games are.