Did Blizzard run their physical card game prior to Hearthstone? How often was there updates to that? I know it's not really a good comparison though.
Excellent question. From what I understand based on our good friends over at Wikipedia, it was run by Upper Deck.
Sets were released as follows:
Heroes of Azeroth (released October 2006)
Through the Dark Portal (released April 2007)
Fires of Outland (released August 2007)
March of the Legion (released December 2007)
Servants of the Betrayer (released April 2008)
The Hunt for Illidan (released July 2008)
Drums of War (released November 2008)
Blood of Gladiators (released March 2009)
Fields of Honor (released June 2009)
Scourgewar (released November 2009)
Wrath Gate (released May 2010)
Archives (released August 2010 - foil reprints from Heroes of Azeroth to Fields of Honor)
Icecrown (released September 2010)
Worldbreaker (released December 2010)
War of the Elements (released April 2011)
Twilight of the Dragons (released July 2011)
Aftermath: Throne of the Tides (released October 2011)
Aftermath: Crown of the Heavens (released February 2012)
Aftermath: Tomb of the Forgotten (released June 2012)
Timewalkers: War of the Ancients (released October 2012)
Timewalkers: Betrayal of the Guardian (released February 2013)
Timewalkers: Reign of Fire (released July 2013)
So about 3 expansions per year which is about right. I understand that we just went into "release," but a lot of us having been playing for 6 months or longer (I started in early October as an example). I'm also, firmly, of the belief that the only reason they didn't release the game sooner was for this type of smoke and mirrors tomfoolery where they can say "New cards? Already? We've only been in release for a month!"