You are kinda missing the point. To have 16 layers on a single component, you would need 32 texture lookups(provided it is two textures per layer, base color and normals). With texture arrays you can have 16 layers on the same component, while using only 4 texture lookups(with a limitation that you cannot blend more than 2 layers at the same place). Think of it as having only 2 layers instead of 16, but you can select freely from 16 sub-layers for both of these layers. So in regards to pixel shader strain, It would be slightly less than 8 times better.