the problem is there isnt in the game a magic dmg for earth things, so they do random stuff mostly resistable
but still lets compare the n1 school of damage dealing
burning hands
cooldown2
dmg 8+4 per shard but HALVED if resisted
range 1
mana cost 10
hurl boulder
cooldown 3
dmg 8+2 per shard, but CANNOT be resisted
range 3
mana cost 22
so basically on cd and ranged they both win one and lose 1
damage is hard to say but you have consider that early stuff usually has nearly no armor, while you may find something fire resistant or immune
also you still can get a random resist with burning hands while you cant with hurl boulder
mana cost is much better for burning
so i agree mana cost could be reduced slighly but not much more than that, this is still a ranged spell and its lvl 1 so not supposed to be that good after a bit, same as with burning hands
and fire IS the dmg school, earth damage spells HAS to be inferior