O’Brien is a “chief,” Jonas and Cutler hold the rank of “Crewman,” and I think those are the only enlisted personnel who have lines and appear in more than one episode. Starfleet seems ridiculously officer heavy.
Is the enlisted/officer distinction different in Starfleet from traditional armed forces? And where are all the warrant officers?
Which does make sense too, since the federation seems to like their ships to be prepared for just about everything, including massive evacuations.