I honestly don't think you're going to see any dual wielding classes in FFXIV.

You may get things like the Pugilist who have animations that use both hands, but I don't think we're likely to see any classes that actually utilize the offhand slot for a second weapon.

My main thought process is that it screws with the loot tables too much. Let's assume that you have a knife fighter that uses two daggers, one in each hand. It now takes twice as many attempts to get your drops to come down. in addition, how is potency judged? is it off the main hand, the off hand, both?

Logistically, there's just no real advantage to be gained here. I'm actually surprised that GLA, CNJ, and THM don't just have one weapon that comes with a matching shield, like the PLD Relic, except all linked to just 1 weapon slot.

In FFXIV 1.0, there was a reason for this. Shields had their own skills that you could learn and you could only use them if you equipped a shield. Very early on this caused a lot of problems for tanks while leveling and it was scrapped, the shield skills were moved into the weapons.