Samurai's magic ability will make those spells far more effective. Knight unlocks a bunch of excellent White Magicks, but has lousy magic power.
Knight has excellent strength and strength-boosting heavy armor, so this combo will greatly increase katana damage. Samurai has very high magic power, along with the magic-boosting mystic armor, but has just mediocre strength. Samurai's katanas do damage based on both strength and magic. Samurai/Knight - Basch - The synergy here is incredible. Even better, you can use the Drain spell to damage enemies while healing yourself. High HP, shields and Main Gauche (a dagger that gives you a whopping 50 evasion) combine with access to all the buff/healing spells to make this the best tank in the game. White Mage / Hunter (Shikari) - Fran - a nearly invincible healer/tank hybrid. You can also easily heal any teammate with dark-absorbing gear by attacking them! In other words, this is THE ultimate Yiazmat killer. Samurai/Hunter (Shikari) - Balthier - Not as strong as Hunter/Breaker but has one huge advantage - this is the only combination that allows for Genji Gloves + Yagyu Darkblade (Dark element weapon) + Black Robes (which boost Dark damage by 50%). This combination gives you 3x swiftness, a decent ranged weapon (hand bomb), all 4 breaks, Genji gear, high strength and HP, and ninja swords. Hunter(Shikari)/Foe Breaker - Vaan - Hunter's ninja swords are one of the best weapons to use with Genji Gloves, and Hunter/Breaker is arguably the best way to do so. Keep both parties around the same level by regularly swapping between parties.
This is the build I'm thinking of going with for my FF12 Zodiac AgeĢ) Access to strong healing throughout the game Scroll down to post #7 to see outcome *** ** NOTE: The build shown in the opening post was greatly altered and improved after discussion.