Speaking of the content, I'm wondering if it's necessary to have an R/M/E weapon in order to be accepted into a Delve party. Most of the shouts I've seen for it are requesting very specific skillsets, which has left me regretting the decision to buy the upgrade. I'm a casual/part time player and would hate to devote so much time to getting R/M/E weapons (or even the +2 abyssea gear) only to have it serve to allow me to get the delve gear.

It seems pointless and frustrating to me.

To the OP, I'd say if you're geared well then you'll probably get into parties for the new content. Otherwise, it might not be worth it.