I just found out, that you cant cast Annulment anymore (light armor skill lines hield), when 1/5 of your light armor pieces is 0% durability.
This only can be a bug, since it makes no sense - I still wear 5 pieces light armor, even if one is damaged. Also the description says "with 5 equiped pieces", not "with 5 equiped and healthy pieces".
PC - EU
Primary: PvP: magSorc, magNB, PvE: DK Tank, Templar Heal
Secondary: PvP: magDK, Templar, PvE: Warden something