Hearthstone Duels is seeing minor adjustments during today's game update, Patch 27.4.2.

Quote From Blizzard

Hero Power Update

Dino Tracking

  • Old: Discover a Beast. Give it +1 Attack.
  • New: Discover a Beast. Give it +1/+1.
Passive Treasure Updates

Starving

  • Old: After the first time a friendly Beast dies in your turn, draw a minion from your deck and give it +1 Attack.
  • New: After the first time a friendly Beast dies in your turn, draw a card.

Corrupted Felstone

  • Old: After you cast a Fel spell, give the left- and right-most minions in your hand +1/+1.
  • New: After you cast a Fel spell, give the left- and right-most minions in your hand +2/+1.
Treasure Pool Updates
  • Starving has been moved to Pool 1.
  • Unlocked Potential has been moved to Ultra Rare.
Card Pool Update
  • The Caverns Below has been banned from initial deckbuilding and all card pools.

Bug Fixes and Game Improvements

  • [Duels] Hunter-class heroes can now be offered Arcane Passive treasures.
  • [Duels] Warrior-class heroes can now be offered Pool 2 Fire Passive treasures.

More Balance Changes

If you're looking for other balance changes, we've got them all covered in dedicated articles based on the format.

Additionally, Hearthstone Battlegrounds is set to receive a few changes in the update and Duels also gets some love.