If the Earth magic arrow is used, and the opponent has fire or air resistance, does the damage of the Earth arrow decrease by half? Is this intended, or is it a bug? I was playing Heroes of Might and Magic Online.
Arrow and Vision do not belong to any specific school. Fire, air, water, and earth resistance affect the arrow. The arrow's damage is determined by which school is better developed. At least, that's how it works in SoD. You can find more details in Fizmig.