According to the bonus chest list and the explanatory text for the 7th chest I was supposed to be getting 2 random and 2 rare items - I wound up with 2 common (guessing they were the random) and... an epic and a legendary. Not that I'm complaining, but not sure chest is rare+ and it's not mentioned? (btw - WOW at clovidian's boots) Edit: List says guaranteed rarity, so guess it's rare+ after all, however when opening the chest it says 2 random, 2 rare.
Yep, that's the minimum you should get. There's a much higher chance for a super-rare as well. I should make that clearer.
