Dual wield when?

[Venur]

Never. There is no such thing as "proper" dual wielding. If you look historically - back when they actually used swords, axes, etc. to fight - nobody ever[*] used two weapons at once. When possible weapon+shield or (rarely) a 2h-weapon was much preferred.

He never made any refference to real life and stated "in fantasy"

But yeah the most used weapon-style of all time is probably the spear+shield.