I don't get it. Why would you want to trash your spoils on this board? I don't see Scrying Pool. There's no Colonies unless you're hiding that from me. They should be a pretty reasonable way to help you buy Provinces alongside your Graverobber shenanigans.
What Ed said. I can use two cards (Graverobber+X) for a Province, or three Spoils. The Graverobbers have the added advantage that they get out of your hand so that you can draw more cards with Watchtower. Without Graverobber, Bandit Camp is an interesting way of picking up Treasure with University.
Cartographer is a particularly good as Graverobber fodder. It's a cantrip, so doesn't get in the way, but it also does a lot of searching for key cards and discarding of Provinces, which is important when you have so many in such a small deck.