I'm playing the Caster of Magic DLC, and the last few times I've played the world has spawned without any orihalcon deposits on either map. All the other DLC stuff is there, and I've seen Orihalcon in previous games, but there hasn't been any in the past few games. Two of the games were set to mineral rich, if that matters, but the main reason I put it on mineral rich was because of the first map that didn't seem to have any orihalcon. Any ideas how to fix this?

Orihalcon is rare, and ore generation doesn't guarantee any specific amount of any specific ore, so it's possible to have maps that don't have some types of ores.
Unfortunately, you'll need to use a save editor if you aren't satisfied with the default ore chances.