I'm also a bit confused about how the tiling works however I'm convinced that is down to my inexperience.
If I'm creating a substance, say a rusty metal, I can use the global material slider and get really nice resolution. However once I start assigning textures to a UV'd object this no longer works as the AO, normal etc all get scaled as well.
So I have experimented with the Transform Material node which does indeed allow me to tile a material, however the resolution is low. Here are some pictures as an example, using one of the standard PBR materials on a rounded cube:
Global Tiling x 1
Global Tiling x 8 (Looks great!)
Material Transform (no tiling)
Material Transform /2 (x3) - Looks pretty blurry