Tips with Nero are keep practicing your Instant Rev (tapping LT or L2 at the right time during your sword slashes to instantly fill 1 of your Exceed bars so your next sword slash is on fire and does extra damage and gives you more style points), mix up attacks (repeating the same one too many times in a row slows or stops style point gains), and use the Devil Bringer more. Use it to bring enemies to you, to get behind Angelos, and use Buster to finish off enemies.
Do something like, Streak into the enemy, do a slash, slash, slash, slash combo, high roller, slash, slash, slash, split, buster.