Technically no, but also yes. It lowers the resistance the target has against your skills, but you can't deal more damage with this if you remove all the resistance. But yes, on most targets you will deal more damage with your Physical, Poison and Disease abilities.
Ahh ok so that answered another question of mine for the DK ultimate that removes all phys resistance with the poison morph you cannot make the target lose more phys resistance by having inc phys dmg penetration. Good to know.