you can be a cunt and still be charismatic
Resolve isn't charisma though, and Durance isn't charismatic. The problem is that they put too many things into one attribute.
Durance has high resolve because him having high mental resistances fits his character.
Alright. But what kind of hero has low mental resistances? Do any of the Pillars 1 companions have low mental resilience? Even Aloth, who is the wimpiest of the bunch possibly, is having to deal with an arsehole living inside his head. You could argue that not going insane from that requires very high mental resilience, and you could also argue that having that arsehole in his head makes him quite mentally resilient. Of course, you can also argue the opposite.
'Mental resilience' as an attribute in a role-playing system ends up being retarded, because what kind of hero has shit mental resilience? A character that keels over at the first sign of trouble, can never make up his mind, is easily persuaded by others, this is not a heroic character.
If you look at the companions in Pillars 1, you could make the argument for every single one of them that they should have high or very high Resolve, because Resolve as a concept is pretty much required for a heroic character. A character with shitty Resolve isn't going to be an adventurer in the first place, they'd just stay at home and work all day on a farm, or tend a bar, or be a homeless beggar.
How can you role-play a Watcher with 5 Resolve? He would fail at every step of the quest, because he'd just give up, maybe go get drunk in the tavern instead.
Anyway look at what Resolve actually does in Pillars 1, nobody gives a fuck about Deflection unless you're building an ultra tank, the other attributes are far more useful. Aside from that, Resolve is useful in conversations, as a 'persuade' attribute.
That's why I said Resolve is effectively Charisma, from a gameplay perspective, if you put the Deflection mechanic aside, which most players do. Except, you can easily imagine a hero who has low Charisma, as someone who either can't talk his way out of a paper bag, or is just unpleasant to be around. Whereas Resolve is basically un-dumpable from a role-playing perspective, unless you want to role-play a librarian.