German sniper survivability is good. I consistantly get snipers in the early game and by the end they have 40+ kills. If you keep them behind and constantly adjacent to grens/mg42 they play a harassing role perfectly.
In terms of the snipers being able to be resistant against mortar fire I completely disagree. Arty or tank rush is the prime method in which I lose my Ostheer snipers. You remove this option from the Soviet player what else have they got to do when this unit is in the hands of a good player?
If you believe your sniper will be targeted by in-direct fire it is time to be more conservative with it, keep it by itself to avoid it becoming collateral damage and aim to remove the in-direct fire threat. I personally have no problems with my sniper and get it the majority of my games.
