I have read many posts where people think the magic system is too bland, and, to be honest, it is.  It does not matter what element you use in battle (unless you have a shard), the effect will be the same.  One would expect different types of magic to have different effects making it useful to specialize in one type.  Here are my ideas on how to make them different.

Lightning: Always hits, no matter what.  Against metal armors does an extra 25% damage (metal conducts electricity).

Fire: Lower accuracy than lightning (base 85%?), will set non-metal armors on fire doing an extra 10% damage and lowering defense by 30% for the rest of the battle.  Only does 50% damage against metal armor but also makes it hot for a turn.  If another fire spell is used while the armor is hot, it does 50% damage + 2 per unit (searing) and lower attack and defense by 30-40% for 1 turn (It's hard to fight when your own weapons and armor are hurting you).

Ice:  Similar accuracy as fire.  Normal damage unless the armor is metal.  If it is metal, it does 75% damage and makes it cold for a turn.  Another ice spell while the armor is cold causes 75% damage + 1 per unit (frostbite) and lowers their actions for the next turn to 1.0.

Rock:  Higher base damage (50% stronger?) than the other elements as it does physical damage and can be blocked using normal defense.

Note that Lightning, Fire, and Ice do not deal physical damage- they deal magical damage.  A unit's defense should have no effect on them, which it currently does.

What ideas do the rest of you have?