Should I keep my shield as-is or try for something else (not much NX left)

I would keep it for now then. Shields tend to be stubborn and 22 S.Cubes isn't a whole lot.
Maybe you could aim for a Critical Rate Inner Ability and then try recubing for a % Boss/% Ignore combo.

I already have a 20% Boss inner that I don't really want to get rid of.

I was hoping for %Boss and %ignore but it's so unlikely

EDIT: threw two cubes on my other shield... first went legendary, second went 40% def ignore 30% boss...


dat luck.

Threw a cube on the other one... 20% boss, 21% total damage. Keep?