Well, the deflection system would still be a single point of failure for the human species. Colonising another planet of the solar system would reduce SPOFs to

Well, the deflection system would still be a single point of failure for the human species. Colonising another planet of the solar system would reduce SPOFs to events affecting the entire solar system - the sun becoming a red giant, a neighbouring sun going supernova, a pulsar setting up shop too close. Settling on another planet removes species-ending events such as asteroid strikes, global nuclear war, a really bad virus getting out, nanotech grey goo getting loose. The deflection system would only remove one of these.