How does a Barbarian handle physical immunes?

[Tommi]

Note that Berserk converts all physical damage of your attack into magical damage. This includes the basic weapon damage, strength and dexterity bonuses, bonuses to physical damage from skills, critical strike, etc. The additional damage of Berserk is also first physical damage, which then gets converted into magical damage. Thus, you may use, for example, might mercenary or laying of hands (vs. demons) to up Berserk's magical damage.

Cheers,

Tommi