Well, I have gotten close. I got 7 last week on my mage. He ended up getting a 502belt out of it. So I was wandering, has anyone here gotten enough keys to open all 8 of the chests yet? If so was there a purple in at least one of them?
Chest contents are random, so you could get an epic with just one key if you're lucky. There's no guarantee that there'll be an epic in at least one of the chests every run.
Honestly though when you think about it there really should be a chance you'd get an epic off at least one chest. This would make it that much more epic knowing one chest(at least) holds an epic and you need to use your guess wisely.