The Lashers are animated with blend shapes and skinned with bones. I could not use VATs here since the material vertex shader applies after the skinning, and would produce incorrect results. The solution was to use blend shapes, which apply to the mesh before skinning.
This is some behind-the-scenes footage from the General Office in my previous post. For lighting, I do not use GI or lightmapping, the entire scene being lit with only a few omni lights.