Dorian frowns, but doesn't dispute Bull's point. He knows that Bull is good at what he does--at what he used to do. It doesn't mean that he has no reason for concern, however.

And he doesn't need to say that he absolutely hates the idea of being out of contact for it to be obvious. His expression sours, eyes narrowing and lips pursing. "For how long?" He has to ask, has to have at least some idea of a basic timeframe. He'll worry himself over it either way, but at least he'll have some idea of when Bull should return, or when he should begin looking for him if he doesn't do so in a timely manner.