A level 80 warrior creature has 9729 armor. C=15232.5. So, the cap is (9729+15232.5)/3=8320.5. Let’s say a player has 30% armor penetration from armor penetration rating and no other modifiers that complicate the calculation (talents, Battle Stance, Sunder Armor, etc.). The game chooses the minimum of 8320.5 and 9729, so 8320.5. That is multiplied by 30% = 2496.15, and so that much armor is ignored. The effective armor on the target is 7232.85 (9729-2496.15). From a player point of view, the armor penetration rating didn’t ignore the full 30%, but instead ignored 25.66%. (85.5% as effective as expected).
These equations should help you be able to test and verify that Armor Penetration Rating is working correctly and as we designed. The tooltip is not actually inaccurate, as it states: “Enemy armor reduced by up to 30.00%.” That "up to" is key.
Please be sure to test without any other effects which modify the armor calculation (Battle Stance, Sunder Armor, Mace Specialization, etc.) as they may involve other systems that add additional complexity to the calculation.
En substance
qd on dit (en brut c'est a dire unbuff) que la pénétration d'armure est de 30 % c'est faut car selon la formule
si le boss (lvl 83)a (reprenons l'exemple) 9279 d'armure il faut appliquer la formule suivante soit
(9279+15232.5)/3=8320.5 le jeu va donc choisir le minimum entre 8320.5 et 9279 pour calculer les 30 %
soit
8320.5 * 30 % = 2496.15
donc on enlèvera en armure 9279 - 2496.15 = 6782.85 soit d'armure restant
Donc le score réel de pénatration d'armure est de 26.90 % (les voleurs et c'est bizard on trouve pas les même chiffre non plus)