The camera tumbles in relation to how far the look at vector goes (unless you have a 2 or 3 node camera). Maya's doing exactly what it should be doing, you just have to hit that f key more often to get the camera's "pivot" to be where you expect it to be. The camera's pivot is actually in the center of the camera where the viewplane is, if you use the rotate translation tool you'll see what i mean, while if you select the camera and hit the modifier tool, you'll see where the look at vector ends (the false "pivot" point).