We've got some post-expansion launch balance changes arriving in a data-only hotfix today to lower the power level of Death Knights, Demon Hunters, and Paladins.

Additionally, there are some adjustments to the Arena pool and bug fixes for the main game, Duels, and Arena.

Quote From Blizzard

ARENA UPDATES

Card appearance rates were adjusted. High power class cards for Death Knight, Hunter, Mage, Paladin, and Shaman will appear less frequently. High power class cards for Demon Hunter and Warrior will appear more frequently. The Countess, Fel’dorei Warband, Deal with a Devil, and Astalor, Bloodsworn are no longer be able to be drafted.

BUG FIXES AND GAME IMPROVEMENTS

  • [Hearthstone] Fixed a bug where Sketchy Stranger would only offer 2 options if you were playing as a Secret class.
  • [Hearthstone] Fixed a bug where cards gained by Fight Over Me were not tagged as copied from your opponent.
  • [Hearthstone] Fixed a bug causing mouse-over tooltips to sometimes disappear. This bug fix includes a temporary mitigation until the next full client patch.
  • [Duels] Fixed a bug where Scourge Strike was sometimes literally unplayable.
  • [Arena] Fixed a bug where new Core Set cards were not in the eligible card pool.