since almost no mob use debuffs that really affect gameplay i dont think that the materia is useful now. i bet when we get more debuffs and they actually become worth using, we will get mobs that aslo use them and we will need to build a strategy around resisting a certain debuff. in 11 for instance you would have a fire resist set or a slow resist set or a sleep resist set for certain bosses. now everything is kinda still zerg fest so having those resist sets isnt worth it