I can add a verbosity slider, but it'll be more of a suggestion to the AI than something that can be enforced. If you're talking to Gareth or Oriana it's just part of their characters.
i have the same thing w me. usually their responses are so long it literally needs two or three scrolls to finish what they're saying, and that actually becomes a problem when after that an action occurs like when they follow me the dialogue arrows disappear. but right now im being given some short responses, like (action) "one sentence dialogue", and that's with celandine, who from my interactions with her I wouldn't say is as limited as oriana or gareth