Optus's routing mostly goes via Singapore because of their ownership being SingTel (the state phone company of Singapore)...
I guess each companies routing has its strengths and weaknesses but Telstra do have Telstra Global which has been buying new companies like PacNet which provide them with better access and connection in new areas....
I don't live in sydney, but I know a few people in that area, so I will see if any of them have swapped to the NBN on Telstra... with the NBN as it is owned by NBN Co, only NBN Co can do any work - if the speed is related to a fault - but my Telstra connection here is sitting at 100/40Mbps and even during evening peak (6-9pm) is lucky to go below about 85/40Mbps...
Yours just seems very strange as it looks like that area is mostly Fibre to the Property, which has had less issues in most rollout areas (compared to the FTTN 'thing') but if that is congestion that is the first area I have seen with equally horrendous congestion on uploads as on downloads... normally the upload sits about where it should even when congested...
It is also worth noting, that I just checked Telstra service status page: http://servicestatus.telstra.com
and it shows two current issues with NBN connections in that area, so that may be a part of your issue too...
| NSW | NBN Data | Some customers maybe unable to access their data services or use the internet via their Telstra Broadband Services on the NBN. | 10 Feb 2016 15:21 | TBC | |
| NSW | NBN Voice | Some customers may experience difficulties making or receiving voice calls via their Telstra Voice Services on the NBN. | 10 Feb 2016 15:21 | TBC |