Social Skills: Roll, then Role Play

[Quertus]

I tend to build systems where rolls are not used to evaluate success or failure, but rather are used to obtain information that can be used to determine how to change the argument in the direction of one that would be successful. E.g. the duke can never be persuaded of something that taken as a whole just sounds like a bad deal for him. But if you succeed in a roll, you get to know what you'd have to offer in order to get what you're asking him to do. And if you succeed on a higher DC, you get to know the exact minimum you'd have to offer.

Very much this. Game designers, take note!

We mix it up, but I like the roll first approach.

When you roll an attack, you're testing your characters ability to swing a sword.
You don't force the player to describe the series of feints and cuts she makes to force the opening which lands the hit. You roll against the skill of the character and then describe the result.

Likewise when you make a social interaction you're testing against the character's ability not the player's.
An eloquence bard with expertise in persuasion is going to know the right things to say in a situation where the player is likely to bumbling tongue-tied fool. Setting the DC post-facto on the basis of the player's description is punishing to socially awkward players who want to play a socially competent character.
Likewise a perceptive, inquisitive rogue should be able to investigate a complex puzzle based on the skills of the character not the description of the player.
You wouldn't set the AC of an enemy based on how martially proficient the player is.

Yea and no.

Any system worth playing the fight, you don’t just “roll combat” - you’re “testing the player” with what they attack / what maneuver they use / what Spell they cast / etc.

Similarly, you “test the player” with their approach. And you don’t “punish the socially awkward player” - you set the same DC for Westly’s “to the pain” speech as Wat’s “fong you” blunder, as they’re both “threats of physical violence”.

So, absolutely, Character skill tells how far you can get. But player skill tells what direction you’re headed.