Most people in this game who set up and hard scope aren't focused on radar as much as they should. They don't even relocate after kills. I can't tell you how many times I've flanked snipers that hard-scope from one spot. Inspect their sniper. If they don't have 3rd eye, you can get them. If they are completely decimating your team, you must get them to a) move b) change strategy or c) worry about being flanked. If you don't take over their post or get them moving, you don't have a chance. If you're not in their line of sight and they know you're coming, the only thing that should matter is your own gun skill. EDIT: and grenades. if you know where they are throw grenades.