Before you say anything, I know I'm not going to get the same performance under WINE as in Windows.
Now, I've been getting really poor performace with running WoW: Mists of Pandaria, and it's not just 10 or 20 fps less, it's literally around 100-200 fps or more.
I've tried running it with D3D and OpenGL, and the only difference is D3D has a lot higher options for some reason.
When running in Windows I get about 80 fps with ALL performance settings maximized / set to the highest value possible. When running in WINE I get about crash / 30-60 fps on the absolute lowest settings.
Here's all the PC info:
Motherboard: GIGABYTE 970A-UD3
GFX: Zotac GTX 660
CPU: AMD FX 6300 3.5GHz
SSD: Samsung 840 120GB
PSU: Corsair CX 600M
RAM: Corsair Vengeance 8GB