Concealment and vorpal

[Giridan]

So I'm level 13 bard and I have 6 mythic tiers. I have a cloak of displacement. I had my cloak active and a high level/mythic tiered NPC with a vorpal weapon rolled a 20. We didn't roll for my percent miss. (Because I just had it constantly going for the fight). But would having the concealment cause any disadvantage against this?

[Secret Wizard]

Yes. Natural 20 just means the attack bypasses your AC, but your miss chance still applies.

[blahpers]

Vorpal isn't really relevant to this problem. Miss chance applies even on a natural 20; so do rider effects like vorpal.