the Precursor has less resistance than the 3 million, i found this out when adding spell penetration cp on my sorc, after adding penetration above (still below 18000) the damage did not go up.
Step 1 take note of your resistances (Spell and physical) (A)
Step 2 Use the Berserker Strike ulti
Step 3 take note of your buffed resistances (Spell and Physical) (B)
Step 4 subtract A from B and the remaining (C) is the resistances of the target.
Berserker Strike
Strike an enemy with a vicious blow, dealing 7389 Physical Damage.
This attack ignores the target's Resistance and grants you Physical and Spell Resistance equal to the amount ignored for 8 seconds.