Lightning, Fang, and Hope have probably the strongest combination of primary paradigm jobs for most of the fights the game throws at you.

I used Sazh more early on for Haste, but haven't used him recently.

If you were targeting a specific fight, you could maybe make a case for using Sazh, Vanille, and/or Snow based on a particular job strength (like Sentinel for Snow) or a unique weapon bonus, but in general I think the versatility of Light, Fang, and Hope over the course of the great majority of battles makes them the best combo.