Let's not forget that the All Whites played such few internationals that Herbert really didn't have a massive window to try out younger players in regular international football. That part I don't think is his fault, as he doesn't make the schedule. (Someone can correct me if I'm wrong on that)
Qualifying for the Confederations Cup would have been helpful. As well as the 3 pool games we would have also played a couple friendlies right before the tournament. Herbert's job was to ensure we qualified.