Hearthstone is making some balance changes to respond to recent concerns from the community about the state of competitive play.
The changes were detailed on the Hearthstone Blog. Most notably, the Old God card Yogg-Saron isn't having any of its stats changed, but will function slightly differently. Whereas its random spells effect would previously keep going unless it killed one of the players, it will now stop casting spells if it is destroyed, silenced, transformed, or returned to the player's hand.
This comes after the community complained that the game was becoming too random, after Yogg-Saron was used in high-profile tournament matches. You can read more about the design process that led to Yogg-Saron in our Making of a Hearthstone Card feature.
Other nerfs are aimed squarely at persistent complaints about the strength of a few aggressive ("aggro") decks, especially Shaman. Rockbiter Weapon is having its cost increased from 1 to 2, making it more difficult to attach to a Doomhammer for a massive 10 damage in a turn. Tuskarr Totemic can now only summon basic totems, rather than more powerful ones like Flametongue Totem--another complaint of randomness having too much sway on the outcome of a game. The neutral card Abusive Sergeant is having its attack reduced to 1, making it less likely to trade up against other minions. This will also impact the popular aggressive Warlock decks.
Warrior's Charge is getting some of the most severe changes, going from a 3-mana cost down to 1-mana, but only providing the charge effect without the boost to attack, and disallowing the minion from attacking heroes. That effectively kills a recent Warrior combo that allows one-turn lethal. Blizzard usually stamps out strategies that do not allow the other player to respond. Warrior is also having its mainstay Execute increased from 1-mana to 2-mana.
Finally, Hunter's Call of the Wild is being increased from 8-mana to 9-mana, in hopes that it will tone down its power and not overshadow other possible Hunter deck types.