When playing Arena in Hearthstone, there are really only two questions: How should I build my mage/rogue deck or how will I get by if I didn’t get mage or rogue? Blizzard is aware of those two class’s dominance in the format and will take steps to address that issue in a future patch.
The plan is to certain cards from the Arena mix: overused cards for mage and rogue and weak cards for the other classes (except paladin, which receives no changes). As Blizzard’s Dean Ayala puts it:
“We’d like to avoid removing strong spells and weapons from the Arena, because they add to a lot of the unpredictability and excitement surrounding the possibilities outside the current board state. We’d also like to avoid removing iconic cards, since they are generally versatile and familiar tools to veteran and new Arena players alike. Additionally, we can remove lower-performing cards in order to make room for a class’ more commonly utilized cards to show up more often in your Arena draft.”
This tweaking of the Arena card mix likely represents just the first step in Blizzard’s attempt to rebalance the format. Ayala says the team is looking at other solutions, such as adjusting the rates that cards show up and drafting by card rarity.
You can find a full list of the removed cards in the dev blog on the Hearthstone site.