Problem #1: Sydney, Sao Paulo & Buenos Aires are not accessible in a two engined aricraft from JNB - ETOPS
Problem #2: Boeing 777-200LR cannot operate at anything near MTOW from JNB due to tyre speed restrictions
Problem #3: Beoing 777-300ER will carry large weight restrictions out of JNB to most long haul destinations
Problem #4: All the ultra long haul destinations would require tech stops so there goes any time advantage (this applies to LAX, NYC and PEK)
So geography is also a real bitch ... whatever anyone says about the Airbus Tupperware they do a very good and efficient job out of JNB relative to any two enigined aircraft! Maybe there was a reason why SA went Airbus!