I don't want to make Magmasaur's nest spawning fully custom - i.e. modify it beyond some critical bug fixes. By standard WC rules, the closest nest spot within one kilometer is chosen. A nest is spawned there if some extra checks don't fail (like player-built structure limit). CI has _very_ bad spawns in general, and most of the spots aren't really reused. I'll make sure to add custom experimental spawners to the area though.

To the second part of your post: I'm not sure what exactly do you mean. If you meant volcanic X-dinos: they should spawn, but it's all RNG. And limits set by WC don't help with the situation at all.