After 60 hours I'm on level 10 with 2 lone wolf. One has 43 FIN (plus one point in Persuasion so 48), the other 39 INT.
I have failed every single persuasion check so far, usually against people with far less than half my points. Not once have I beaten it (even retrying).
I don't mind losing sometimes (and perhaps it is a dice roll not a direct comparison) but to lose every single time means I either don't understand or something is wrong.