I never play a Barb and built a GF Barb. He's Zerkin and going okay,
but I am curious if a Physical Sunderer would help

thanks again what a great knowledgeable forum

Zerk deals magic damage so no a physical sunder will do nothing for you. If you decide to use e.g. ww or frenzy it will be you'd be better off with a source of amp or decrep.

Magic sunder will work but you would be better off just using 1 point in like ww or conc instead for the very rare magic immunes.

Zerk for mfing bosses ww for everything else.

How phys sunder would help you against PI mobs when you play Berserk Barb ? Do you whirl as well ? Or did you just smacked your skill points to somewhere and thought that ” Berserk ” sounds funny, using it and didn’t read at all skill description ?