All of the personality disorder diagnoses are really, really problematic--but since we're talking about what's in the DSM, I hardly think you can say, when looking at the checklists of symptoms, that borderline has more to do with extraversion than histrionic does. HPD is pretty damn externally-focused--not that BPD isn't, but HPD seems moreso to me.
im not sure why - histrionic is merely expressive - someone who has a seductive personality, who is openly emotional, etc.
I could get into it more, but I dont even think being histrionic is pathological, its more like personality traits that annoy certain kinds of people. It merely means being dramatic, for the most part. You could potentially see this in IxFx but I would agree its more of an F thing.
To me histrionic personality disorder is just sexist, finding sexually confident women threatening even while similar behavior is encouraged in men, and it would be combined with expressiveness of emotion, that bugs some people, they call it emo now, but there have always been femme fatales and flaming gay men and strippers and I think even the old gothic movement was pretty theatrical at its core. So was punk.
BPD on the other hand is entirely external, the person with BPD doesn't have a stable sense of self, acts out, hates being alone. Besides people with BPD are pretty sick, the ones Ive known.
I think people with HPD are usually more highly functioning and may be written of as annoying or entertaining, depending on who is around them.
BPD needs to stay in the DSM far more than HPD or even NPD.