It's entirelly up to you! Really relic is only glamour and a set of achievements so it's really a case of how much you want either (I gave up on relic at the book stage too, as I couldn't be bothered continuing on - the achievements are meaningless and the later appearences of PLD relic look awful so it was a no brainer for me). And this is for every tier of relic for each expansion - when it's released it's pretty powerful, but quickly becomes overshadowed by new (raid) gear and just becomes glamour.

So it's up to you if you want to do it or not, there is no content that specifically requires it.