About one out of three MTA express buses failed to depart on time, according to a report the city controller’s office released Thursday. Auditors who surveyed service on a dozen routes between October and December 2013 observed drivers leaving earlier or later than their scheduled departures 30% of the time, according to the audit by Controller Scott Stringer’s staff. Commuters whose trips were delayed had to wait between six and 28 minutes to get on the road, according to the report. The MTA said in response that adherence to schedules is less important than maintaining an even flow of buses. The controller’s report did state that from a “customer’s point of view,” 84% of buses were on time, in that commuters didn’t have to wait more than five minutes for a bus.