The card itself in only good if you can abuse it such as with an Upheaval
Unlike firebending cards, you retain the mana so you can throw a Yargle under the bus to get out a Crackle with Power, or you can pour mana into Ozai's activated ability, which interacts with cast-from-exile synergies
For Affinity, it was equipment, highlighted by Skullclamp and Cranial Plating (which wasn't itself banned but certainly helped create the insane Affinity decks that led to mass bannings)
it's a disadvantage, and a big one at that
Every card here can be played alongside regular, non-Final Fantasy cards
From Burnished Hart to Oblivion Stone to Nevinyrral's Disk to Skullclamp and all equipment to Sensei's Divining Top there are tons of ways to build around and abuse this