I just beat the final boss of the game with a 5-star rating, first time. It was actually quite easy if you know what to do.
Firstly, you want to make sure your monsters are leveled up, it makes battle A LOT easier. I had a level 36 Flanitor to heal, a level 20 Dragoon as my commando and a level 24 Pleuston as my ravager.
You also want to make sure Noel and Serah are leveled up well, making sure Serah is a level 99 ravager and Noel is a level 99 Commando. For equipment, i used iron bangles and a magicians mark for Serah. Noel had a power wristband, a silver bangle and a grimoire hat. I recommend playing as Noel and using potions to heal if necessary as the hat increases the amount of health you will heal.
Now for the Paradigms, these are the ones i used:
Rav, Rav, Com Relentless Assault
Rav, Com, Med Diversity
Med, Com, Med Discretion
Sab, Syn, Med Evened Odds
Rav, Rav, Rav Tri-disaster
Com, Com, Com Cerberus
You will probably want a paradigm with sentinels though as the boss can do some strong attacks.
When you get into the battle use Relentless Assault against the two weak monsters and kill them as you would usually kill a monster, they aren't hard at all. Now when jet comes out you will want to use Evened Odds to buff your party and de-buff him, don't spend a long time doing this though as you will waste time. After that, stagger him and keep using ravagers until his stagger bar is around 600%, you then want to use a triple commando class to damage him.
He will summon the two weaker forms again so just repeat the process but if you don't kill jet on this second turn, restart the battle as your won't get a 5-star rating. Heal when you need to and use Noel to heal with potions. I won the battle in around 8 minutes with a target time of 11 minutes. You can also play on the easy difficulty if you want.