Who uses Offensive Magic ?

[Moon Rabbits]

Well, take a look at Fran's gambits and see for yourself:

Ally: HP < 50% -> Cura
Foe: Status = Reflect -> Dispel
Foe: Status = Oil -> Firaga
Foe: Fire Weak -> Firaga
Foe: Ice Weak -> Blizzaga
Foe: Thunder Weak -> Thundaga
Foe: Wind Weak -> Aeroga
Foe: Dark Weak -> Darkga
Foe: HP > 10,000 -> Graviga
Foe: Closest -> Bio
Foe: Any -> Attack
Ally: Any -> Shell

[kurosaki_ichigo]

Wow thats a great gambit, i mean on my first playthrough all i had was Closest foe=attack and i made it through fine......well almost

[ValiantKnight]

most of the "weak" gambits come far too late in the game to be of a significant boon unless you delve deeper into the sidequests. They are quite helpful though, at times.
Seemingly quite a few optional bosses use physical immune quite often... and you are encouraged(and in a few, forced) to use magic.