Just focusing on the Gen 3 Competitive context as it's its most splashable, the typical OU Psychics weak to Shadow Ball are;
-Celebi
-Alakazam (barely)
-Medicham
-Jirachi
-Metagross
There's already an issue. Jirachi, Celebi, and Metagross especially all have 100+ base Def. It is genuinely...