Oracle is kind of hard to rank because it hasn’t quite yet landed on a solid role. Honestly though, you’re usually better off with other damage dealing classes such as the much more reliable, and similar, Warrior.
The Berserker lives up to its name by often being uncontrollable glass cannons. This is especially true in FF: Tactics where its abilities were just not that useful or reliable. The Knight class has always been the sad little brother of the Paladin and other, way cooler, tank/attacking classes. Although with a TON of work it can become powerful in the War of the Lions version of FFT.
Sure, it’s not terrible, but normally you want to upgrade it to something else as soon as you can. The Onion Knight and Freelancer is usually always just the basic default class that can do a little bit of everything. However, the amount of effort and skill often needed to unlock and use this class is usually just not worth it.
Listen yes, the Mime has the potential to be an incredibly powerful class.