[Saber Cherry]

Fire immunity was taken from Fire Plate because it made the fire resistance ring worthless, for the most part. Fire resistance is fairly easy to get, from various cheap 1H weapons, accessories, a helmet, a shield, and so forth - and as mentioned, fire is only armor-piercing, not armor-negating. Lightning resistance is much harder to get, copper plate gives slightly lower protection, and lightning is armor-negating. 50% lightning resistance is almost useless in many cases where 50% fire resistance is very valuable.