I feel its totally unfair that the Capt/FO who did the check in this particular case is should be lambasted in any way..
I don't agree. I wouldn't choose the word "lambasted" but the unlatched cowls really should have been spotted during the exterior inspection.
For the record, I am a current Airbus TRE (and an ex-BA training captain) and have flown several thousand hours on the aircraft with both V2500 and CFM engines. The nature of the V2500 cowl latches is no secret. The flight crew member doing the inspection really needs to get down to check them. That used to be strongly emphasised to all converting pilots during line training.
It was dinned into me during my tyro days as a pilot (in the RAF) that one should never assume but always check. It is, after all, one's own pink body up there, not the engineer's. I'll leave it at that.