Revokers are a sideboard card because you won't always be playing against Deathblade/Stoneblade decks. It takes G1 to figure out what you're playing against and G2 & 3 and that's when Revokers come in handy. It's only when you frequent a shop weekly and know who the attendees are and what they play do you usually mainboard Revokers. So there are some exceptions. I don't go to shops frequently so I keep them sideboarded.