NVIDIA isn't the only one with a new driver for Assassin's Creed Unity, AMD issued its Catalyst 14.11.1 Beta driver for this new game. You can download the driver over here.
This release enables peak driver performance optimization for AMD Radeon™ graphics users in Call of Duty®: Advanced Warfare and Assassin's Creed® Unity.
Call of Duty®: Advanced Warfare performance optimizations
Assassin's Creed® Unity performance optimizations
: Occasional stuttering in Assassin's Creed® Unity in CrossFire mode under specific game settings
: Small chance of intermittent screen tearing or corruption in Call of Duty®: Advanced Warfare on high settings 4K resolution in AMD CrossFire™ mode
: Quad CrossFire AMD Radeon™ R9 295X2 may sometimes black screen when loading a game in Call of Duty®: Advanced Warfare
: AMD Radeon™ R9 280X/280 may experience a crash when playing Call of Duty®: Advanced Warfare and a video at the same time. If you experience this issue a work around is turning off the video while playing the game.
: CrossFire users may experience intermittent flickering in Call of Duty®: Advanced Warfare menus. As a work around if this issue is seen restarting the game may cause the issue to disappear.
AMD is currently working with Activision to resolve the following issues in Call of Duty®: Advanced Warfare:
Users in AMD CrossFire™ mode sometimes experience texture corruption
Negative scaling sometimes being observed at specific resolutions with AMD CrossFire™