Again, Relic Nexus will have barely no use...

[mero-ix]

To get the Poetics weapon, though, you need to be clearing T11 (?), and you need a good weapon to help get you there, ie: Nexus. Except, if you're on Final Coil, you're clearing T9 and can just use your T9 weapon which is nearly as good as Nexus anyway. Which means Nexus is basically only worth the grind to benefit your epeen and standing around in Mor Dhona with it out.

(For the record, I do have a Nexus (actually, I nearly have two) and I'm also on T10 and thus far it has not been worth the grind to have a Nexus for clearing content, so I will admit that it was only done out of boredom/completionist/epeen.)