Check out this great Facial Rig for Maya from SoukiZERO who is a Character TD supervisor at Motion Magic. He shows how he created the interactive controllers for his Facial Rig that was based on FACS (Facial Action Coding System) in the videos below.
Suuki notes that it can get really expensive to create warp deformers for every single controller. Maya will slow down considerably.
The facial rig shown in the videos is available for purchase from TurboSquid. The Maya facial rig is based on FACS, and has interactive controllers with over 100 joints that deform the model. No Blend-Shapes used at all.
Also included with the rig are skin wrinkles. They use a custom DX11 shader that can blend normal maps and displacement maps with masks.