I came here just for the jester, and it's not on the list
The sage class was pretty weak as well.
If we take the mechanics of that particular class ( later kit?) aside, the concept of a jester background / rogue / bard subclass is sound.
i found a new respect for the jester in a medieval wedding « MCed » by a jester where I was invited a few years ago. Because that’s what jesters were: MCs, wedding signers, entertainers, presenters, and ad-hoc referees.
in a high medieval settings where the king’s court is in great parts composed of brutish lords and knights (and their wife’s and daughters), the best person to enforce courtesy is the jester. Because the famous but brutish knight can not afford to look more ridiculous than the king’s clown in front of the whole court. If someone’s too loud, too impolite, too out-of-place, the jester intervened by setting the example (often in a tongue-in-cheek or sarcastic kind of way). You’d look stupid if the jester was more courteous, respectful of women, well-spoken, and composed than you. So the jester forces you into your best behaviour because you (most likely) aren’t as witty as he is, AND he’s protected by the king/lord who is more than happy to have someone enforce manners for him.
Then the jester is an entertainer, playing music, juggling pins or whatever, or introducing musicians/entertainers. If the court was a show, he’d be the opening act, the master of ceremony, and the stage manager at the same time.
After supper there would be games of brawn and agility, again introduced and refereed by the jester (who at this point is likely to be the only sober person left). The jester would challenge the strongest, rig the games for the weakest, ridicule those who weren’t nice before, praise the winners and cater to the drunken knight’s testosterone and ego, giving them (at last) an opportunity to challenge / beat / punch one another in relatively harmless ways.
All this for the entertainment of the lord and lady and their court. A good jester would be able to do all that without getting killed by a frustrated knight or an annoyed lord, making him probably the smartest man in the court. A jester’s INT is as important, if not more, than his CHA.
An adventuring jester would take these skills at judging people, playing to their ego and needs, and wit their way out of trouble with them in their adventuring life. Not the most efficient dungeon delver, but an excellent social guy/gal.