In all honesty, it has been the general theme of most RPGs that magic can do area attacks much easier than melee. My biggest pet peeve is that Mages get AoE for no cost and AoE is not available on melee classes. My suggestion would be to make all magic single target, balance that from there, then add AoE at 3x MP cost and balance that (should be pretty balanced with the 3x MP cost). This lets other character do physical attacks, and then if they want to hit an area, use spells.