Earlier today, we learned about the Overwatch loot box drop rates in China, revealed by Blizzard as required by new Chinese law. Now we've got the same information for Hearthstone, which appears to dole out its best stuff at a slightly slower rate.
The Google translation of the Chinese original, as always, is rough, but it works out like this: Every Hearthstone pack will contain at least one card of "rare" quality of better; "epic" cards will appear at an average of one every five packs; and "legendary" cards will turn up at a rate of one every 20 packs.
The rates are pretty close to what players have already established independently: This thread from December 2016, for instance, references previous research determining that legendaries drop at a rate of one per 18-20 packs. What's interesting is the very last line, which Redditor Czhihong translated to, "actual odds of getting better quality cards will increase in tandem as players open more packs."
That would seemingly confirm the existence of the so-called "pity timer," which basically increases the odds of scoring a legendary the longer you go without one. The existence of the pity timer isn't a secret by any stretch, but it's still nice to have it and the drop rates, officially confirmed—even if, as with Overwatch, we can't be absolutely certain that the same rates apply outside of China.
Now if someone could only do something about pulling the Paladin Quest twice in a row.