FWIW the COMAND NTG 5.5 in our W205 (with live traffic data and latest maps) is similarly poor at routing on small country roads. We have it set to 'fastest' and the arrival time regularly drops when we ignore the directions close to home and take a different route instead. In contrast the TomTom we use in the Vito (also with live traffic and latest maps, and set to 'fastest') generally selects routes we know to be the quickest when approaching or leaving our local area.