I decided to start trying to farm for Elite Orbs in Sewer Stash, because I've heard that it has a (relatively) large drop rate for them. I played about three times earlier, with no lucky drops, and I started thinking that OOO might have changed the drop rates in that mission since 2013.

But then I gave it one more shot a few minutes ago, and when I came up to the first group of five Treasure Boxes, I got THREE Elite Orbs, like nothing. Just a few days after I got a Surge Breaker Shield from a Treasure Box.

Yeah... I think I'll be coming back to this mission quite a lot.