The Heroes of the Storm website does not specifically announce the launch of Blizzard's MOBA, but it offers several articles surrounding the release of the free-to-play game, which is now officially out of beta. There is a discussion of the future of Ranked Play and an update on Team Builder Facebook App Issues as well as word on rewards for Hearthstone players and World of Warcraft players. They also announce Johanna Hero Week as they celebrate the launch with the addition of the game's newest hero, based on the Crusader class from Diablo III. Here's Blizzard's overview of the game:

Heroes of the Storm™ is a raucous online team brawler starring your favorite Blizzard characters. Build and customize heroes from across every Blizzard universe to suit your play style. Team up with your friends and engage in fast-paced mayhem across varied battlegrounds that impact strategy and change the way you play the game.