Invasion doesn't have a PL, Gowther does. And Invasion is many things, there are different techniques with different effects.
I think Blackout Arrow should be more powerful since it's not AoE but let's ignore that. I don't know Escanor's Sprit stat, but are you saying that it was below 400? No way. We have seen a simple move like Rewrite Light work on people like Galan, who had 2000 in Spirit, so what does it say about that?
I know that it affects the nervous system. That's not my point. Moves like Nightmare Teller for example directly damage your mind and soul, it doesn't affect your nerves, which is something physical, the soul and the mind are not physical.
Lol what? Then what represent the magic stats of Gowther? he clearly has a PL.
He could be below 400, 500 or 1000, like I said, we don't know his spirit stats but you don't need to have a monstrous spirit stats to be powerful, your magic and physical stats are enough.
Sure it worked on Galand, but it is nowhere close to Cath who has 5000, even the best fighters in the verse don't surpass Cath ( canonical speaking ) in spirit power.
I am saying that he should be able to do better due to that fact.
Well any technique related to mind, soul, brain control, etc, your spirit power should be able to resist it with enough power of course. Spirit stats are here for a reason.