OS: Windows 7 Ultimate x64
This appears to have worked for me but bringing my average latency down from over 500ms to an average of 220ms as of tonight
This may be a fix, or it may have been something Blizzard did in last nights patch, or a combination of the two but here goes........
1 - Open the Network and Sharing Centre
2 - Open the Local Area Connection that you connect through (myself, I use 2 network cards (NICs) so I did this for both)
3 - Open the properties of each NIC and remove the tick next to "Internet Protocol Version 6 (TCP/IPv6)
4 - (Be very carful in here) Open your registry editor "regedit.exe" and navigate through to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\TCPIP6\Parameters"
5 - Creade a new DWORD called "DisabledComponents" (case sensitive)
6 - Edit the new DWORD and give it a value of FF in HEX
7 - Reboot PC (this is a must for any changes in the "CurentControlSet" registry area)
This will disable and completely block all TCP/IPv6 network tunnels and adapters and have found that my constant, in game, latency is now 205-220 from Melbourne
Please try this out, and if it assists you, please pass it on to any and all D3 fanatics :o)
If it does not work, please let me know via a reply here, I have may other tweaks to add to this one that may all need to be enabled to create one big tweak
EDIT: If you like, I can try to make an instructional VID and post to youtube if people have problems following the above