Basically dual wielding is never worth it for anyone.
You need Two-Weapon Fighting style on a Fighter or Ranger to get your ability modifier to off-hand damage.
Then you need the Dual Wielding feat to be able to use weapons that aren't light and for +1AC.
But the main thing is that the Bonus Action off-hand attack competes with so many other things in BG3 you often won't even use it, i.e. every time there is a Shove opportunity or you need a potion.