the drk relic is better than ruby, this is not up for debate. Without materia, sure, the ruby weapon's crit and det beat out a stock combination of woeborn's ten and crit, but the fact you can meld 300 more substats of your choice, whether that be all det or a combination of det and crit, or d.hit if that's your thing, then there's no comparison especially when you consider that the substats don't really differ all that much in how strong they are.

Tenacity doesn't make a weapon awful, it's just a little worse off than det. Meld that stuff on, and it's better.