I think interview is just formality .The CCE GB depends on test marks..300 marks of interview will not make any difference because interview marks were given average in the past.If you are lucky to by choosing scoring subject like Islamic history or political science you will manage to get allocation otherwise if you have chosen subject like IR or Public administration you are doomed ..This is my words base on experience by checking the DMC of many failed candidates..Those who have IR and Public Ad will not get allocation