Mainly because it doesn't work against mindless enemies.
- Kayano Sayaka: the very situational +25% resistance to Nature doesn't even count as an effect. Vampirism, however, is good for monsters with high DPS, like Ren and Air, and it will give even Roheyu additional opportunities to restore health. However, the less damage a character deals, the weaker the effect. Often, regeneration would be better if you had to choose.
- Gisela: simply the best universal effect. Essentially, Gisela enhances by a certain percentage what is already the strongest stat in the game.