The problem is only restricted to TWF if you use spotlight balance and shoehorn classes into definite roles (eg rogue skill monkey). If you want a rough damage balance - like the core rules come with (ie no MCing and no feats) - then everything becomes a problem with the +10. Those who use GMW and SS do too much damage, and those without it do too little. If my goal is to keep the rough damage balance the core rules provide, the best and most convenient fix is obvious.
The best and most convenient fix is obvious, give rogue a feat and fix Dual wielder.
If you want a rough damage balance - like the core rules come with (ie no MCing and no feats) - then everything becomes a problem when some fighting styles have a feat, others have a bad feat, and a few styles have no feat at all.
The second you add any option (MC, feats, templates, boons, magic items) to the game, rogues and mages fall behind. There is no way to boost Sneak Attack nor spells. Every Class with Extra Attack or Multiattack will take any bonus damage or accuracy better as they can stack the same bonus 2-5 times.
Even at -5/+5, a blessed up warrior probably leaves a rogue or mage in the dust for single target DPR.
The contest between single attackers, mages, and multiattackers is a losing one.