Originally Posted by
Voidmaster
That is not a WoW engine limitation, the WoW engine does extend to multiple cores if one core is on 100% load. This limitation comes from Dx11, Dx11 supports partial multithreading only. With Dx12 you can properly multithread your graphics stack on OS level, but they can't fully implement Dx12 yet cause like 90%+ of the playerbase has a GPU that does not support Dx12 on feature hardware level.
To allow full multithreading without Dx12 would require rewriting the entire game engine, something that isn't going to happen.
If you are this bothered about it you can solve it yourself though, just get a CPU with high Single threading performance (e.g. no AMD CPU, but an Intel Kaby Lake CPU).