Which jewel is best for berserk barbarian? Or neither? Berserk is weird since it takes physical damage you would deal and turns it magical.
Does Berserk benefit from only half of each jewel? (The +% enhanced damage from Protector's but then the -% magic from Guardian's?)
Assuming you are using Grief and so your protector's stone will be in an armor piece... the ED will not work. It's an old bug, see the red text on here:
https://www.theamazonbasin.com/wiki/index.php/%25_Damage. So unless your protector's stone is going in your weapon (which it probably won't be, because Grief exists), protector's stone is kinda bad for berserk.