I agree with what some others have posted.
With the current classes, I don't see dual wielding swords happening since class and weapon are linked in this game as it would require a new class.
Dual wield via paired daggers/short swords would most likely be implemented with a Thief class which could potentially evolve into Ninja and Dancer as jobs.
As far as parrying daggers as off-hand items that potentially increase parry instead of block, I could see that being implemented with a Fencer class that could evolve into Red Mage and Runic/Mystic Knight Jobs.