Chaosmancer
Legend
For me, the disconnect here is really that it's feasible to masterfully deceive someone without any "social combat" at all. Combat as-is exists as a stand-in to simulate actually stabbing and battering another being, whereas I can run a succubus that plays PCs against each other unassisted, maybe with a Deception roll now and again if her behavior ever comes under any serious scrutiny.
Sure, but you don't need to use social combat all the time. We don't necessarily roll initiative when the PCs drink poisoned wine, we roll con saves, but those aren't solely combat based mechanics. You can still run that succubus the exact same way.
But then, when the players have a strong suspicion she is a succubus, but they don't want to just stab the woman whose been "helping" them, you could have this as an option for that confrontation. "you guys can engage in a social combat, giving you greater chances of success since it is more than a single roll, but if you fail, you guys accept she isn't a succubus."
And if one player raises a stink "NEVER! My character will NEVER believe she isn't a succubus no matter what the dice say!!" Then you can try and compromise with the player about what consequence they are willing to agree to, or have them sit out the social combat if they will agree to no reasonable consequences.