Is it every enemy period? Or every enemy you hit excluding merc? Or if on weapon every enemy you hit with weapon excluding spells? Also, I found a griffons eye on useast ladder if anyone wants to trade.
It depends on how the penalty is applied. If it's from conviction or the lower resist curse, it's an effect placed on the enemy, so everybody benefits from it. If an item just has an ability like "enemy lightning resistance reduced by x%", its applied to the wearer, so nobody else will benefit from it.