AMD Catalyst v12.4 will not support Diablo III
Players are recommended to roll back to the v12.2 drivers.
Diablo III fans are strongly advised against upgrading their AMD graphics card drivers to the latest v12.4 update. According to Omrakos, an AMD support forum agent, the latest drivers are not compatible with Blizzard’s mouse-destroying RPG.
There is a massive thread you can follow here. The short is, both v12.3 and v12.4 drivers are not compatible with the game. Those that have already updated are recommended to roll back to the v12.2 drivers which are known to work perfectly with the game.
You can download the v12.2 drivers from here. Users are recommended to perform a ‘clean install’ before rolling back. This entails using Driver Sweeper to rub all signs of an AMD driver from your PC before installing the driver again.