Would Percival have been able to 2RKO Roartz with the hammer in order to save the energy ring? The hit rates would be even worse, but if Rutger and Zealot can kill Henning with a 0.01% chance of success, then hitting with the hammer 4 times in a row doesn't seem impossible, however unlikely it may be.
EDIT: Percival with Armorslayer: 20 Strength + 2(Energy Ring) + 8(Armorslayer Might) - 1(Weapon Triangle Disadvantage) = 29 Attack before the Armorslayer's effective might bonus.
Percival with Hammer(w/o Energy Ring): 20 Strength + 8(Hammer Might) + 1(Weapon Triangle Advantage) = 29 Attack before the Hammer's effective might bonus.
So unless I've messed up a calculation, which is possible, then Percival should be able to 2RKO Roartz with the Hammer without the need for the Energy Ring, at obviously horrible hit rates of course.