Looking back at DOS it was similar. Dual wielding starts out stronger but two handed weapons become much more powerful as you go on and start getting talents or spells that boost crit chance or let you increase AP. It's kind of like the old "linear warrior, quadratic wizard" idea.
That's not to say dual wielding is worthless. The main advantage of dual wielding is being able to stack multiple elements and status effects at the same time. Having a poison dagger and a fire sword can be a deadly combo if the enemy fails both saves. It also let you hit more often which is a big deal when enemies have shields or very high defense/evasion. Sometimes you only need to hit for 80 damage and that 400 damage warhammer can't get near him.
