Case 1 - Wind Druid:
Shall I put a protector's stone in my helm (or any other piece of gear) - would it boost the tornado damage as it's physical? Would my tornado do more damage to the enemies because of their lowered physical resists?

Case 2 - Berserker Barbarian:
Shall I use a protector's stone or guardian's light to boost the damage?

Any ideas?

Protector stone seems BiS for most physical builds. That fade is also great. Unfortunately I keep finding the frost one....

Wouldn’t it be better to use guardians light on zerk build as it converts the damage to magic? Enemies would have lowered magic resists?