Don't worry, Hunter's aren't getting nerfed, at least not yet. A new update is available for Hearthstone: Rastakhan's Rumble, with a few changes to Rumble Run, the singleplayer campaign introduced with the latest expansion.
One of the biggest changes is an increased chance to get cards that have bigger synergy with the Shrine you choose but also added card offerings. According to Blizzard, these changes will "strengthen the experience of fighting in the Gurubashi Arena, allow players to get to know the nine troll champions, and give each run its own strong theme".' Some of the Bosses decks also got a few adjustments, so that the game is a bit fairer.
The Arena also got a few changes, mainly in the appearance rate of each individual card, so that the win-rate for each class gets closer to a 50% rate. You can get further insights on these changes over on the official website.