There are divisions by type of crime (financial, terrorism, government corruption, capital murder) but these types of crime often overlap and thus require overlapping resources and personnel from a DA's office...and someone has to be the person who decides how and what to allocate to each case.

This is not much different than police departments, which have separate departments for patrol, homicide, burglary, vice, internal affairs, etc....no matter how the squads are organized, there is still a chief and/or a commissioner who makes the policy and management decisions and who makes the official public statements.

  | Would it not make more sense to have them segmented
  | by type of law, since they're all arguing in federal
  | courts anyway

She probably has many specialized areas under her, but she's at the top of that particular power structure.