Fishguard services a failure? As seen
here, the increase in passenger numbers over the first year was similar to the consultant's estimates. I think 45,334 passengers at Fishguard compares quite well with Pembroke Dock (Passengers: 48,644, Pop.: 9,753) and Pembroke (Passengers: 31,622, Pop.: 7,552) which have a more frequent (though slower) rail service).
I'd be quite supprised if the estimates from either consultant were based on a timetable which still featured two huge gaps (09:56 to 13:30 (3.5hrs) and 10:57 to 16:xx (5hrs)).