In patch 8.1.5, we are making some improvements to how World of Warcraft uses DirectX. In essence, our old DirectX 11 is now called DirectX 11 Legacy, and our new DirectX 11 is multi-threaded. More details on each DirectX version is below:
DirectX 11 Legacy
A single-threaded rendering backend. This is provided to be the most compatible with older hardware, operating systems, and drivers. This is also the least performant. This is very similar to the functionality of DirectX 11 in 8.0.1.
A new multi-threaded rendering backend using DirectX 11. This should improve performance for older GPUs or operating systems that don’t support DirectX 12. This is new for 8.1.5.
A multi-threaded rendering backend using DirectX 12 for hardware, drivers, and operating systems that support it. There are some performance improvements in 8.1.5, but it is mainly the same as the 8.1.0 release.