Might be worth mentioning the awesomeness of Tunnel/Loan
I've had difficulty in getting Loan to discard a Tunnel. You'll often just hit a Copper or other Treasure instead. I suppose you can avoid buying Treasure to up your chances of revealing a Tunnel, but stalling your engine in the hopes of getting Gold wouldn't put you out ahead.
Tunnel/Loan/Tomb?
It makes it better, but probably still not enough.