Due to new regulations regarding digital goods being sold in China and their strict crackdown on potential gambling possibilities within interactive entertainment, Blizzard and other companies operating in the region have been forced to reveal the loot box probabilities in games like Overwatch.
The announcement was made, in Mandarin, over on the official Chinese Overwatch website for those playing the game in China. Eurogamer provides an English breakdown of what the post contains, stating that Blizzard has announced that in compliance with China's national laws regarding loot boxes and the risk of appearing as gambling, they've revealed the drop rate chances for various items in the supply boxes.
On average, each supply box you unlock or obtain in Overwatch will come with four items packed inside, including ornaments or game currency. The quality of the items will vary per box, but each supply box will contain at least one item of "excellent" or higher quality, and on average the supply box will will provide an "Epic" item at least once every 5.5 loot boxes.
The odds of getting a "Legendary" item in Overwatch increase dramatically from 5.5 boxes for an "Epic" to 13.5 loot boxes. So that means for every 13.5 loot boxes you acquire, one of them thereafter will likely contain a legendary item.
Eurogamer questions if the loot drop ratios in China are the same for other regions, including Europe and the Americas. It's a good question because this would give you an idea of what your chances are of getting something decent in the game.
It's also interesting that China was the one to actually take the step to regulate RNG loot boxes in games. We expect as much from low quality mobile games, but for full priced AAA games, it seems somewhat anti-consumer to have RNG loot boxes that can be purchased for real money and you have no idea what's actually inside.
In this case, Blizzard revealed the loot chances (obviously to avoid any penalty of being labeled as running a gambling ring), but it's still technically gambling if you're trying to get a certain item but it's random as to whether or not you might actually get it. If you could simply buy what you wanted from the cash shop then it completely solves the problem and a game like Overwatch clearly couldn't be considered gambling.
However, forcing people to have to spend money or grind out in hopes of possibly getting the items they want still seems pretty much like gambling, since it's not really up to the player (or how much they spend) that determines if they can actually acquire that item. Many games use this method of item distribution through cash shops, and there was a multi-billion dollar gambling circuit centered around the Counter-Strike: Global Offensive skin trading market, where gamers would spend real money in hopes of rolling a random high-quality skin.
Most commenters on the Eurogamer article didn't seem to mind the odds of rolling an epic or legendary item in Overwatch, but most still felt as if options should have been made available so there's no random purchasing of loot boxes in hopes of getting an item, but instead the items should just be available in the cash shop like in World of Warcraft and other MMOs.