Agreed with Changelle.
Heartstone IS Pay2win, but it fades away once you've played in over 2 months or so.
Look at it this way:
2 completely new players begin to play Heartstone.
The first one uses money, the second one doesn't.
After, let's say 10 hours, they're going to 1v1.
The first player has bought multiple packs, created a deck with rares and legendaries.
The second player has bought maybe 5-6 packs, with only 2 rares in them.
Who will win? - The guy which paid of course (Unless RNG takes over the game completely, which is less likely).
Just giving my 2 cents ^_^