Docents you equip provide armor equivalent to Full Plate. This is treated as metallic heavy armor. You have damage reduction 2/adamantine, a 35% arcane spell failure chance, -5 armor check penalty to certain skills, and a +1 maximum dexterity bonus.
Note: Evasion doesn't work for Warforged with Adamantine Body since it is considered a heavy armor. MRR/PRR is granted to the player when the feat is purchased. Equipping/Unequipping your docent will not change your PRR/MRR