They can’t really though. That’s the messed up part. They are main tanks that just can’t play main tank because they work so well together that they had to nerf the pair of them.
The only way to nerf them separately, would be to disallow the selection of another, after one is selected. Then that would imply double standard rules for tanks. Then the complaints about ONLY tanks having double standard rules would show up, so DPS and Support would need a MAIN dps and a MAIN support. Eventually it’ll be main tank, off tank, damage dps, utility dps, main healer, utility healer.
I for one didn’t sign up for that.