Actually you can.
If you had seen how more expirienced players are using sniper you would know. When the time come to shoot he is switching to sniper, then jump left or right, and as soon as he is on the ground he already have locked his target and now he just fire, if he miss or if there is more enemies he is switching to secondary weapon and start to fire and strafe until he hide itself for a bit in order to be able to prepare for the next sniper attack.