I have tested this quite a bit I've had the deck since just after Vilis first released and it's one that my playgroup fears and is one of my personal favorites.
If you build a Vilis deck, be prepared to
fend off a lot of early attacks, your opponents will learn very quickly to get their attacks in before Vilis hits the field. This is one of my favorite decks to play, when it works, it works amazingly, when it doesn't its still a blast to draw as much of my deck as I can.
MVP cards are definitely the ramp cards the faster Vilis hits the field the faster you can get your
game plan going. Aside from that cards like
Ashes to Ashes,
Reckless Spite and
Wicked Pact that kill two things and draw you five cards are really useful as well as cards to help get your life back to keep spending it such as
Gray Merchant of Asphodel, Kokuso, the Evening Star, and
Exquisite Blood.
Not of this World is a necessity as no one who goes to spot remove Vilis is going to expect a free counter from mono black.
Hope this helps.