I quoted Ysayle cuz she seemed to be a special case among primal invocations but I guess it's more complicated due to those plot holes as you explained

But indeed, I think Arcadion's fighter would be closer to reaper's enshrouded as I guessed. And I agree with you, it's an absurdly dangerous job. But to me it's dangerous because of the avatar link. Not that I want a lore reason for everything, but what other part of the job could be dangerous with the reaper ? Its basic skills with scythes makes it a basic fighter, maybe with its dashing skill when it jumps through its gates ? or its black energy spheres ? I'm not this much familiar with that job