October 1st patch notes:
It has been modified so that when you use two-handed swords, or two-handed spears, the max damage of the skills used would increase by 10%
2H weapon users are rewarded for dropping their shield/dagger and giving up that defence and offhand damage.
Consider this when making your builds.
Yeah but at the same time its not true for archers where a crossbow/pistol combo outdamages a 2h bow.
Sorry should’ve mentioned that this only applies for Swordsmen 
Fencer got it better +15% rapier damage when not equiped with shields. but base damage of 2hand swords and spears are higher.
Fencer’s attacks have a narrow area and are more suited to single targets rather than a group of enemies. This might make grinding pretty inconvenient.
However,
This is the ultimate key that separates 2H weapons from 1H weapons.
however rapiers 5% advantage in damage when it comes versus flat damage.