Composite maps do not seem to work in the bump slot. It seems to only pick up one layer in the stack, however, they do seem to work with the VrayDisplacementMod. Is this a limitation?
Bump maps are not supported with procedural textures (this might be helpful Chaos Docs).
Ok I didn’t think that the a composite map was considered a procedurel texture, since It’s just mixing two jpg’s together I just noticed there is alot of features considered procedural textures I always reference that link but I think it needs to be clarified on what procedural textures are not supported in the bump.
Thanks.
You are right that we need to clarify better what procedural is. In practice, everything that is not only a bitmap is considered procedural.
That would help..I got around my issue using a VrayNormalMap to mix two textures in the bump.
So are procedural maps going to be supported anytime soon? I remember asking Vlado about noise in the bump slot at Siggraph 2012 he said it would be working by the Vray 3 release.. just a little over due. 
We have working solutions, it is that the results do not match the production render and I believe this is not going to work for most of the users, so we are still looking into it.
A working solution is better than no solution.. maybe adding it for the nightly builds?
I will try to get more feedback for with we have from our 3D teamonce more. Max uses totally different approach for calculating bumps, if the results are much off, the solution could be more annoying than working, I am afraid.
We are still looking into it, if I have something new I will post it here.