[Edi]

Actually, Ring of Sorcery, Ring of Wizardry, Skull Staff, Skull Face will boost a D4 mage to D8.

As far as Hidden in Snow vs Spectral Mage, an Unfrozen Mage has the potential to hit W3E3D3. It has D1 and 3x 50% E random, 3x 50% W random and 2x 50% D random. A spectral mage really doesn't hold a candle to that in potential. I've routinely had Unfrozen Mages that had 2 lv 3 paths and one lv 2 path, and you can get up to three mages per casting. Given that water gems are not that useful for a lot of other things besides certain items, 55 for Hidden in Snow is not bad at all.