First, thanks for reinforcing my doubts :) I'll just have to do something with those fire-conjuring, earth-shaking barbarians, I guess. Something different from beheading, anyway.
Second, thanks for the suggestions about the mind/body thing. I haven't thought of that particular division so far, though I used to have a three vs three division in one culture (as far as I remember it was kind of a good(ish)/bad(ish) type division between Shadow/Fire/something else and Light/Water/something else). Not sure why I've abandoned that, but it's certainly worth keeping the idea in reserve. (Yes, the Usual Four are the other four. Wasn't feeling extremely radical back when I first made this up)
To be honest, I don't think my Shadow really should be among the grounded ones. It includes buried memories, dreams and the like, so to me it's pretty metaphysical. Of course it's all very far from settled, so far that I'm wondering if it ever WILL be settled :)