Well those completing their Relics come Heavansward may have it much much easier then it is now so might be worthwhile holding off on other Relics if you want to do them.
Is it however worthwhile completing it once Heavansward is out? Probably not considering 3.1 or 3.2 may see another Relic again.
I think people misread about those with Zeta, there has not been confirmed that i know of to be an advantage only that "those with Zeta will be taken into consideration"
However should there not be an advantage? Some of us started Relic before atma drop rate increases, etc. it was hell so we were kind of testers for SE in a sense and now they have made it easier.
I truly hope dungeon drop rate is increased in todays update, it is just a horrible horrible quest. My first Zeta was bad but now for my blm it seems 2x worst