Great Circle Mapper, quite correctly shows the distance from Melbourne to Johannesburg to be 5582NM. The EDTO rules applied by VOZ, hasthe aircraft remaining within 1340NM of a useable airport. Coasting out over Geraldton, you can route straight for Mauritius, followed by a slight dog-leg towards destination. Not as inefficient as it seems, as you are staying away from the roaring forties more often than not. Of greater consequense is that the return flight from JNB-MEL doesn't get to take advantage of favourable tailwinds to the extent one would desire. Some payload restriction out of JNB for ultra long haul is a fact of life, regardless of type. The economics of the 300ER is still VERY hard to beat!