To be honest, at small stations, it should be accepted as one of those things. Some customers will need 10 minutes or more and though it's extremely frustrating to wait behind them, there's not much that can be done about it.
On the odd occasion that I have been a time consuming customer, I have offered to stand aside to let people behind me get their quick tickets. Other times, I have been told to wait by the clerk to give other people a chance.
Nowadays, I almost never buy anything at the ticket office and only buy tickets available from the TVM, or order online and pick up from the TVM. If I need a remote ticket then I can buy it online from the Southern website and pick up within seconds and I usually have my laptop on me so it is usually not a problem. If I need something that can only be bought from the ticket office, then I won't travel by train, unless I can get the ticket in advance. Missing the train while queueing is not worth it.
Not having remote tickets on TVMs is frankly disgusting. TVMs in Netherlands, Germany etc. enable you to buy any ticket from any ticket machine. In fact, you pay extra to buy tickets at a ticket window in NL.