If you opened a bunch of card packs from the new Hearthstone expansion, The Mean Streets of Gadgetzan, within the first few hours of its release, then you might have noticed that you were getting a whole lot of duplicate cards. Well, it turns out that this time everyone who claimed the game just seemed to have it in for them was actually right, as a bug was causing a greatly increased drop rate for certain cards. A hotfix has been released by Blizzard and all packs are now distributing cards evenly according to their rarity.
The bug was increasing your chances of receiving tri-class cards, which are a new type of card in this expansion that can be used by specific trios of classes. There are nine tri-class cards in total — three commons, three rares, and three legendaries — which means that if you opened a substantial amount of packs, you were pretty much guaranteed to end up with way too many copies of the common tri-class cards.
In order to correct the issue for players who had already opened their packs before the hotfix was released, Blizzard is adding free packs to those players’ accounts equivalent to 33% of the total packs that they opened, regardless of how they earned the packs that were opened. So if you opened 50 packs at release and are confused about why you have 17 mysterious new packs to open, that’s why they are there.
If you bought packs when the bug was still in the game but haven’t opened them yet, you will have no issues with card drop rates, as the hotfix has corrected all unopened packs.
While this isn’t an exactly comparable compensation, it should be noted that you get to keep all the cards from the packs you opened before the bug was fixed, so players should actually end up with more than they payed for since they can turn all those duplicate cards into dust to craft new cards with.