Hm, I don't know.
It worked fine on the way to LV2, because you actually got Poisoned and Darked often enough to make it level up before the enemies started to love Curse, but it was a way too large leap to the other status magics later in the game.
I guess the game is designed so you need to fight lots of enemies in order to survive in Mysidia land, and therefore inevitably will have a good use for the spell lots of times.