I for one applaud Blizzard. They heard us loud and clear after Diablo III: "We will not buy another Blizzard title until you earn our trust once again."
Clearly this was the only way to lure in the fans who didn't want to be burned by another $50+ mistake.
Who really cares if it is pay-to-win? It's free. If it is terrible, we know Blizzard gave up. No tears. If it is surprisingly good, well, they just might save enough of a fan base that their next big thing won't flop.