So I played a game with this over the weekend (though I didn't win), but I feel that if worked better, it could be very viable.
It's pretty simple. You play Pillage, it gets trashed, you scoop it up with Graverobber, and put it back on top of your deck to use next turn. Rinse and repeat. Even better if you got Graverobber when someone else went for Pillage - you never even had to pay for your Pillage!
Would definitely be boosted by Schemes, to make sure that Graverobber is always there.