If I got a couple extra percent damage over mediocre mages from all my hours of practice, muscle memory building, experimentation, and math, I’d stop playing mage.
Mage doesn’t scale linearly either; I point this out every time people complain about mage. You can’t do more than 3 afflictions at once, which do 3-4 fireballs worth of damage from a single cast, apply weakness, and make up a significant portion of your damage. Afflictions are a bigger boost to slower mages, who have a higher max afflictons to fireballs cast ratio, so we get diminished returns to speed from that.
The only reason I can see for people to want everyone to do the same (within 10% ish) damage as each other is so that everyone can clear the same content, regardless of skill. This isn’t how the game should be and defeats the purpose of improving yourself to beat the hardest enemies.
Make the other classes more rewarding; don’t make mage worse.