Of course. Getting through immigration in Vietnam is very dependant on several factors; your time of arrival as you say. You could be unfortunate that your flight might be running slightly late and has landed after a bank of international arrivals, it could also be that you are fortunate enough to land ahead of those arrivals. HAN is the less busy of the two main international airports, with fewer international flights than SGN, but that's not to say you should expect arrival formalities to be smooth when you are flying in Business.