I don't know why everyone is so down about Blizzard on balance. When it comes to their competitive MP games they're probably the company that has the best balance out there. WC3/TFT wasn't 100% the most balanced game in the world but it was balanced enough that all four races had a chance of winning in any matchup. Brood Wars was a fantastically balanced game even if that was a bit of happenstance and KeSPA pushing wildly imbalanced maps to try and shift favor depending upon the current dominate race. SC2 is probably the most balanced competitive game to date with win rates being at worst 45/55 in given matchups. Heroes of the Storm cycles some meta shifts and sure there are a few clear cut winners and losers but that is a given with pretty much any MOBA. They have really increased their content delivery pace as well with a new hero every 3 weeks and a large balance patch every 6 weeks. If they can adapt that kind of pipeline to Overwatch the delivery could be rapid and high quality.
Then lets talk about continued support. Even on games Blizzard hasn't implemented a F2P model they continue to balance the game years after launch. Heart of the Swarm is even being talked about to get a balance patch despite Legacy of the Void coming out later this year. I wouldn't want any other company really handling a potentially competitive game like this.
