Idk, man. I have DE Sidious above Valkorion at this point, (though on the same level/in the same tier), but it ultimately comes down to where Ziost puts Valkorion in relation to Sidious, as Elm said. If the Ziost feat is like ROTJ Sidious tier, then I think the case can be made that FP Valkorion has parity with DE Sidious.