Wow I think the progress bars / tokens for the rare, epic... cards is a really good solution.
I don't really like the new ranking system but I already hated the reward & potion change before: I have hundreds of potions that I'm never gonna use because I don't buy that many packs. So it always feels so empty and useless when I open rewards and only get potions,
The token system reminds me of the League of Legends system. They too made it harder to earn the in-game currency to buy characters but they added some extra "shards" rewards that you could collect and use for skins or characters.
It was really hard to get enough of them for anything but just knowing you actually could use them in the future for something really nice, a nice skin or extra character, made you feel good about getting them and made collected them worthwile.