Your assessments of the similarities and differences between the classes is totally off base.

Moves that are "similar" between classes aren't the same, they are complimentary- in that using both of them provides a much better effect than using 2 of the same. For Instance, Succor + Medica 2 heals directly for the party, puts up a shield and a Regen effect, the shield gives the regen effect the time it needs to get people out of a danger zone (if the direct heals weren't enough). While Dragoon, Paladin, and Warrior have a basic 1 2 3 attack that gets stronger; the Dragoons does the most damage but doesn't add extra threat. Paladin's applies a Str debuff, and being the highest threat move means it's always up, while the warrior's damage debuff is on a completely different combo that does no extra threat, and competes for time with another combo that lowers enemy defense. Like the Warrior/Unlike the Paladin, the Dragoon will not spam his 1 2 3 combo because he has to manage different debuffs with positional requirements for max effect.