Unfortunately the DSG is better in almost every way..

That is not true. If you are good and fast enough you can use the Gauss in short to medium ranges as well. With weapon pro you can quick scope for a body shot and switch to a sidearm for the final bullet. Problem is the over the top damage from the 71, even if you are quick down to the milisecond that thing will still kill you. Lucky thing is that most people that spot you with a sniper rifle wont care enough and will go straight for you at close range which is an easy headshot.