I do know how the specifics of how these rankings are calculated because they're publicly visible[0]. I'm not arguing that behind the scenes Hearthstone's matchmaking isn't sophisticated enough (although it probably isn't), I'm arguing that publicly, the public mechanisms for determining rank are really bad and encourage bad play habits.
Hearthstone ranking is not a good proxy for skill, it's a good proxy for the amount of time you have to play and the speed of your deck. Objectively, the best strategy to get good ranks at Hearthstone is to build a fast, >50% win-rate deck and then to grind. That's not a good proxy for skill.
> As players win games in ranked, they gain League Points, also more commonly known as LP. They also lose LP when they are defeated. Upon reaching 100 total LP in a given division, players enter a promotion series to try and get to the next available division.
> Players must win a majority of their games in order to advance to the next division. Promotion series within certain ranks, like Bronze III to II, are a best-of-three series. From one rank to the next, such as Silver I to Gold V, promotion series are best-of-five instead.
> If a player doesn’t win that amount of games, then they’ll need to get back to 100 LP to try again.
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Yes, the exact details of how your MMR is calculated is kept secret, but it doesn't matter if you still know exactly what you need to optimize for: winning sequential games, often in chunks, and going out of your way to avoid losing streaks which can result in demotions.
Arguing that hiding the exact MMR formula means that players won't alter their behaviors to fit its approximate contours is like arguing that because Google's page-rank algorithm isn't public that SEO is not a thing.
(Some of) the consequences of this setup include:
A) losing matches becomes much more costly, which exasperates the problems League has with feeders and trolls, and lends itself to a more toxic environment.
B) Experimentation and learning new heroes is best done off of the ladder until you feel like you're competitive with that hero. Experimenting on the ladder is not only bad for your rank, it's also likely to get you reported by other teammates as a feeder (see the toxicity mentioned above).
Players are effectively optimizers. If you give them a system with a clear success metric (ie, a public rank going up), they will optimize their play-style to fit that system. Designers often assume players will stop doing this at some point. They won't grind in an RPG because that's boring. They won't bot a competitive game because that's not fun for other players.
Most players don't think in those terms during gameplay (myself included). Thinking that way is hard. As a designer, if you want a player to optimize for creating a fun experience for themselves and others, you have to explicitly build your publicly-facing systems to encourage that behavior.
That's an overview, not specifics and not details (verbiage that first you and then I used). It's a shitty sleight of hand, so I'm going bring this back around and then I'm done with you.
Hearthstone ranking is not a good proxy for skill, it's a good proxy for the amount of time you have to play and the speed of your deck. Objectively, the best strategy to get good ranks at Hearthstone is to build a fast, >50% win-rate deck and then to grind. That's not a good proxy for skill.
[0]: https://hearthstone.gamepedia.com/Ranked