I just received a lootbox that had all duplicates. 2 blues (because I have all available rare loot), 1 white (because i have all available common loot), and 1 purple, but i don’t have all the available epic loot yet. There’s heroes i don’t have a single highlight for yet.
edit:I think it might have been because of holiday loot rolling on a higher priority table when it pops up. feel free to correct me if I’m wrong.
that’s meant to happen.
I know the rare and common were, but i thought you weren’t supposed to get duplicates until you get all of the available rarity. I don’t have all the epic loot available but still got an epic duplicate.
the loot out of the loot boxes is randomized.
i only just started getting my duplicates even though i haven’t got all of the items.
the more items you have for a type of rarity, the rarer it is to get something from that type of rarity that isn’t a duplicate.
I’ve been getting duplicates every event for a few months now, that’s not how the duplicates normally work. I think i might have figured out what my issue was. I’m guessing you can still roll event duplicates while still not having all of the non-event loot from that tier. But yeah, loot from lootbox is randomly drawn from a pool of available loot you don’t have yet in the rarity brackets the were rolled for that box (when the box was earned or bought), to drastically cut down on duplicates. This is a change that was implemented a little while ago. 
I think you nailed it on the head if I’m reading what you wrote correctly.
The rarity brackets are also broken into event and non-event variants, so if you rolled an event epic and had all the event epics you can get a duplicate even if you don’t have all the generic epics.
So during an event there are 8 “rarities” instead of 4.
Common,Rare,Epic,Legendary
vs.
Common, Event Common, Rare, Event Rare, Epic, Event Epic, Legendary, Event Legendary
I do not think that the reduced duplicate system upgrades the tiers of items.
It was my understanding that the intended result is that if you have available of that tier it is less likely to get a duplicate. However, in no way does that mean once you get all commons you instantly only ever get rare or higher and so on.
Exactly
The specific confusion for this thread though was he got a duplicate epic when he didn’t have all the epics. The clarification though was that he got a duplicate event epic, while he had all the event epics, but was missing a generic epic.
From my experience the reduced duplicate system takes it a step past making it unlikely to get duplicates and makes it near impossible to get them, unless you own everything in the item’s respective bracket.
if that is the case then the other persons post about the dupe tiers having seasonal separate from generic is the most correct answer then
The bigger question is:
If you have all the event epics and legendaries but you still have non-event cosmetics unowned, why on Earth you get event cosmetics as duplicates? Just… why?
thanks for breaking this down. i have now had 9x loot boxes with 4x duplicate. this is infuriating. no way i would buy more boxes knowing this mechanic exists.
update i was at 15x loot boxes before i got a leg skin. i was getting duplicates of my duplicates.