First off, apologies if this is already common knowledge - I just figured it out and I haven't heard it before. Most people know that the weekend Dread Ring daily lair gives you a shot at a Greater Mark of your choice. What I didn't know is that you can run it as many times as you like.

All you need to do is run it like normal, then return to the lair of your choice (depending on which mark you need), buy a key from the campaign store (5k AD and 10 scrip), and re-enter and run it without the quest. The drop rate seems to be about 1/3, so you can get your Greater Mark (plus other loot) for 15k instead of the AH prices of 30k . Of course they're unbound, so you could also sell them, and you'll never run out of scrip as long as you pick up the white drops and turn them in for more at the bounty hunter and run the daily quests.