It doesn't suddenly make you win games though.
When you're first starting out in hearthstone, the ability to netdeck a top tier deck and play that vs playing with the basic cards is absolutely enough to make a difference in your win percentage. Obviously there's no hard and fast rules here, skill matters a lot as well, but all else being equal...
Once again, when I say pay to win in hearthstone, the easiest example of this is to me someone first starting out. Yes. It's not relevant to you or me given we've been playing for a while. But just because this experience isn't relevant to us, and it's something that'll fade away from someone as they play the game, doesn't mean it doesn't exist.
Faster progression is a thing that I wouldn't necessarily say makes a game pay to win, but in hearthstone you play against the same challenges (other people) no matter your level of progression. So, your level of progression absolutely does matter to your win rate, especially when first starting out.
As an aside, do you think my definition is too broad because it doesn't make sense, pay to win means you can pay to increase your win rate, or because it makes a game that doesn't
feel like it's pay to win in a bad way into a game that's pay to win and that has negative connotations? Because honestly, I'd get that second one however, I think it's easier to just say
Pay to win in a ccg isn't a universally bad thing despite the negative connotations it has as a whole.
Then it is to try to weasel around it. (the first one almost feels tautologically true to me... You can almost boil it down to a pay to win game is a game where you pay to win.)
As a double aside, Frost Lich Jaina got "leaked". I say "leaked" because it might not be real, and if it is real it might not be an actual leak but rather a marketing stunt, and either way the hero power didn't get leaked so we still don't know that much about the card except that it's clearly pushing elemental synergy in mage. That could be interesting. Also it would mean blizzard is actually supporting previous expansion mechanics (which when I actually write that out makes me less likely to think it's actually real.)
Edit: For those that don't want go googling for it: 9 mana, summon a water elemental, from now on all your elementals have lifesteal, normal 5 armor, no idea what the hero power is.