The only thing with natural sniping spots such as the water tower in Colorado, the barge in Paris, treehouse in Whittleton creek etc. Is when you kill the targets you need to leave ASAP if the guards surround the sniper nest, you aren’t leaving with your sniper assassin. It’s why I never use the sniper nests, they are too buggy with the guards never standing down, even if you use a fully silenced sniper rifle. It’s always better to find a secluded part of the map with a clear view of one of the targets and use it. Another technique I use is just do a SASO run but shoot the targets with the sniper after knocking them out. Then you can get all classic challenges in one go.