What do you mean by "dirt"? In my editor, I only see this: earth, sand, grass, snow, swamp, stones, Dungeon, stones, water, and tales. Or did you mean earth by "dirt"?

Yes, I just never paid attention to how it's written in the SoD version's editor menu, but in the standalone SoD/WoG editor, it's written as "dirt": see the screenshots.
Regarding Conflux, I agree with you: the doubled Phoenix growth with the Grail makes this city even more unbalanced. However, even with the Grail, you can prohibit individual spells in the city's properties – then the Guild of Mages will give all the spells, except for those you directly prohibit.

In the properties of castles, you can not only build structures but also prohibit them. You can make building a Watchtower impossible by unchecking the "enable" box.

lifemaker, we're not talking about the Watchtower here, but about the fact that the Grail in the Tower reveals the entire map to the city's owner (I hope you've heard about this before? ;)).