Camping a corner with a shotgun gives you coverage of 10 feet... Camping a firing lane with a sniper rifle gives you coverage of a significant portion of a map... You are talking apples and oranges... THe shotgun guy isn't going to get anyone to bite on his setup when you get at high skill levels. But it is unavoidable to not occasionally cross a sniper's fire line, especially if they have multiple snipers on their team. Camping a corner with a shotgun is not going to win you any ToO flawless matches... It's stupid easy to counter this noob strategy.