is there a way to reduce the bump strength on all the textures at once?
many models load in with bumpat 100% with hundreds of textures
one at a time is just not feasable

aww

The "affect all materials" tick box will adjust all of the maps at the same time.
The problem is that if the diffuse, ambient, and specular colors must all be the same for it to work. Otherwise, it messes up the maps on some of the materials because of the black/white ambients.