Don't worry about randomizing. Just repeat it. All the ores I need are there, and I doubt anybody is going to hate me for having te same chunk on repeat :)
I'll do the marble as well, and I may put the malachite down for a waterfall in one of my caves.
also, sometimes things look better when there's a mistake, like the waterfall, but I think it looks ok. What I find is that if you get a backup world and blast some of it, you can see some cool formations, and then do it more precisely on the real thing. We're almost done now, just debugging.