Level-tier is the measure of how the accuracy and defense of equipment is affected. Armour of level 50 is virtually useless against weapons of lv90. In PvP, high level armor is seldom used due to the cost. However high level weapons can often be used thanks the protect-item prayer. Freedom is a lv34 defense capability that is vital for EoC PvP. Reflect, Resonance and Rejuvenate need 37, 48, 52, and 55 Defense, respectively.
It is possible to use potions to boost for these capabilities. Ancient Warriors pvp armour now requires 40 defense. Void at 42 is the lowest level of non-degradable Power Armour. Fremmenik is at 50. It raises the question: is it worth it? EoC PKing is not available in warbands that are not.