Seems to me that some basic customer service training is required - being polite and respecting people costs nothing but creates goodwill that will more than off-set the wait in the queue. Shouting loudly does exactly the opposite, and I don't buy into the arguement about the one-a-year travellers.
My own grouse with T2 immigration is the inability of the same customer service assistants to open and close the webbing barriers depending upon arrivals .... a couple of weeks ago arrived early afternoon and arrivals was deserted but we were directed by the said assistants to walk back and to along twelve or more of the zig-zags to reach immigration. There was no queue so a little common sense would have made all the difference to the arrival experience, but I guess that's a little too much to ask.