The gameplay tweaks after Nexus are great but the game itself ends up feeling moreso tedious, even if you just decide to the Arena only (the main mode). I'd treat it more as an Arena component expansion for Nexus. Still worth playing through all the arena and maybe some training to get nice free parts to transfer to Last Raven!
I'm pretty sure this game never retailed for full price on release anyway so they were at least aware it was just an appetizer, not a full course.

EDIT: I just played Formula Front and that game does the "3rd gen Arena game" thing way better where it has an actual personality. So if you want games with arena vibes definitely go with Master of Arena and Formula Front.