I think world gen is broken. I set mineral scarcity to 40000 (allegedly that's pretty scarce) and almost every tile has everything. I tested it by starting a game on a spot with no aquifer and dropped a 4x4 stair to the bottom. this is what I found. Seems pretty frequent to me.

When I use the basic settings I get lots of tiles with only 1 or 2 metals and no flux layer.

The only other thing I changed from the default was the map size.