Your hard work now will pay off later when more and more upgrades for the relic is released.

Like you said, you will upgrade the stats of the weapon by doing the tome quests afterwards... Sure its annoying to only get a different coloured Relic after an extremely frustrating grind. But might as well get it out the way, eh? If not, stop doing it and do something else (get Levi, COIL or the other i100 weapon) and just wait for the drop rates to be buffed.