Just to clarify myself - I'm using conqueror with absorb and arcanian with def - they dont share CD, they pop randomly, sometimes one after another, sometimes both in virtualy the same time.
Step away from the arkanian relic, those relics are a trick
ALL PVE relics will NOT proc in PvP combat. EVER
Just read the discription it clearly states that it will not procs in PvP
Also if you read those descriptions you will notice that they proc from different sources
Def procs from being attacked
Absorb procs from shielding an attack
If you have a DoT on you that dot might proc your def relic because it is attacking you, however it will not proc the absorb relic because dots are not shield able.
Def and absorb relics can be active at same time however this is unlikely in PvP situations due to the nature of defensive stats in PvP.