TWF does not allow attacking with a one handed weapon and an "off hand" weapon. You'd have to patch the TWF base rules. At that point, assuming my rules for twf, we'd compare 1d6+3+1d6+3 vs 1d8+3+1d4
the 1d4 would have a higher chance to hit and the 1d8 does more damage on "Extra attack" and opportunity attacks. I'd have to calculate how much, but I'd wager that this option would be much better than 2x light weapons. For example a rogue would deal more damage as +1 to hit is quite important for sneak attack.
I wouldn't use it for these reasons. If we were talking about 2x daggers or plain dagger then there may be room for calculations, but not with that much.
This seems like an attempt to fix dueling, but as above dueling doesn't actually need fixing - it's quite good and gives a significantly higher boost in damage than other fighting styles. The issue is that dueling needs a talent/feat. That talent/feat should likely contain +1 AC like Dual Wielder does, but it'd need more.
This stance would be mechanically worse than dueling. It's even worse than Defense.