Every single melee class uses the exact same damage calculation. If their strength, weapon damage, and determination are equal, then 100 potency from class X will deal the same damage as 100 potency from class Y. 100 potency is equivelent to 100% of the strength, weapon damage, and determination calculation. 200 potency is double that calculation. 50 potency is half. The math in the first post is correct.

Berserk is a multiplier on your damage. Your damage is based on your strength, weapon damage, and determination. You can multiply your strength, WD, and determination by 50% then factor in potency, OR you can multiply your potency by 50% then factor in str, WD, dtr. Either way, you get the exact same damage in the end.