A quick and easy way to create a really nice facial rig is to use Blender's bendy bones.

All credit goes to Daniel Lara for sharing his concept regarding facial rigging with bendy bones. Check out his videos on #EasyRigging here:
https://vimeo.com/channels/1100385

Download my Control Bones Creator Blender addon here:
https://bit.ly/2m9Yq3M