I think its being getting worse and worse with each release - It's always been there - Is, in even the best commerical games too - But it used to be only inches to the edge, mostly overlapping WITH the edge of the model, but now you may actually aim well over the edge and still have it hit air....
Its like aiming the Bazooka - I clearly see I'm aiming over the obstacle, but somehow it still manages to hit it and kill me