Those three are my preferred end-game party (probably surprising no one, really). While in general I find it best to avoid leveling secondary roles until the late game (each character’s primary roles get pretty big stat bonuses and the like from the higher crystarium levels), Lightning actually makes a solid Synergist (mostly because she gets Haste). If you’re not planning on any end-game activities, you can probably skip farming for it if you don’t want the grind, though
Something worth noting is that Commando and Saboteur both slow decay on the Stagger gauge (as does Sentinel’s Provoke, iirc, though this is less useful generally), so it’s often viable to run something like SAB / SAB / RAV as an opener with this party, since Fang and Vanille have some different debuffs they can apply while Lightning can work on staggering something quickly. Alternatively, SAB / RAV / RAV works well sometimes, though Fang isn’t as solid a debuffer as Vanille by her lonesome, so I favor the other combo. Either way, this also gets you away from running double-COM, which is usually not ideal, since it makes the two Commandos attack separate targets and most fights will flow better if you pick off one target at a time
I personally don’t like over-relying on Sentinel (outside of some particular bosses or hunt marks). It’s typically only on one of my Paradigms (usually either SEN / COM / MED or SEN / MED / MED), since for the most part you don’t want to spend much time in your defensive Paradigms: drop in, heal up, and then get back on the offensive as soon as possible. I will usually run some form of COM / RAV / MED or SAB / RAV / MED for a more “balanced” Paradigm for fights where SEN isn’t really needed, though