You don't need the relic because you can get a weapon of the same item level for much less effort by beating the current extreme trial. You can get a weapon of nearly the same item level by purchasing the crafted one from the market board.

For a higher item level weapon you can spend 7 weeks doing the normal raids to get what you need, or do the savage versions of those raids.

It's mostly about glamour, customizable stats, the brief times it's actually a better weapon and just giving you a reason to bother doing the content associated with it. If you don't have much time you can settle for the crafted one and you'll be fine.