There's no good reason to hang onto clusters and wait for Omega. With 3 instances, A rank hunts are up constantly. I'm sitting on 21 clusters and 700 centerio seals after using a combo of both to buy 15 VI's. Get in a hunt LS and go spam them. Even doing them casually you'll be rolling in clusters.

Granted you don't NEED VI's for doing EX primals but there's also no reason to sit on them when you're drowning in clusters/seals. Prices on them are going to bottom out fast as more people realize how easy they are to obtain.