Larian's RSP system works against traditional RPG stats check. RSP is a game of chance, stats check means certainty. like the Spider Queen encounter, that's how traditional RPG works, only if you have 5 in Charisma can you win any argument over her.
imo, a better and more inline with overall game design is stats/skill check: charm -- charisma check, intimate -- STR (or CON?) check, reason - INT (or scoundrel?) check. some NPCs are more vulnerable to certain kind of persuasion type, and some situations call for certain type.
