Starting at the same time, I've had issues with creating a new custom deck. After choosing a hero and selecting the "Choose" button, which then takes me back to the screen with my full card collection.
A third issue which has surfaced simulaniously is a lack of any visual to accompany entrance into the queue for casual or ranked play. I can hear audio for the "slot machine" style graphic, but no other visual than a complete grey screen wash.
Finally, a fourth issue to pull it all together, after the battle is decided and Victory/Defeat is shown, no visual is shown and the loading time has more than doubled since these four issues came to town.
Using Mavericks on a 2009 15" MacBook Pro.