I think you have MPCs back to front 
They are for when you want to control a lot of material instances with one parameter.
Dynamic material instances, are for when you want to have parameter control over each instance individually.
At any rate, that expanding sphere thing is a post process effect, not a sphere mask on a mesh.
Naturally, I can’t find a vid about it right now, but I have used that sort of effect. Will hunt a bit further.