He does he compare in the current meta for dps on global? I. E. Noctis, luneth or gilgamesh etc?
I understand part of the appeal of orlandu is that he's good for building up chains while you have a finisher to make the final blow. I guess it's too early to say if yun can build up a chain?
I'd say he's probably within the Luneth and Gilgamesh range but below Noctis. However, that highly depends on what TMs you have. It gets a little complex because it really depends on what other chars you're running along with them.
If you equalize it and make sure they all can Dual Wield then he's equal to Luneth and Gilgamesh in just attack modifier. Spearhead should be about 375% after you calculate ITD. Setsugekka should be 360% after ITD for Gilgamesh. Blazing Combo for Yun should math out to about 360% after ITD and the Fire debuff as Blazing Combo is innately a fire attack.
However, that's looking at them individually. Within the context of a team, if you can get an elemental debuffer and equip Luneth or Gilgamesh with a weapon of that element, then they'll beat Yun. Setsugekka becomes 540% roughly while Spearhead becomes like 600%+ or so. They'd have to sacrifice a bit of attack for it is the only thing.
Noctis is 450% after ITD and is a lot more flexible with weapons so he can get an elemental weapon on no problem.
Edit: Orlandu's attack is easy to chain, -50% Light debuff and has a strong modifer that equals about 400% after Ignore Target Defense calculation. In addition, the Excalibur is a pretty standard TM, so his attack maths out to 600% Attack modifier normally. When you combine all that, he can easily element chain to make his damage skyrocket like crazy. He's in that sweet spot between pure chain character and a finisher character which is why he's strong.