I see you posted this on Whirlpool as well which is a good idea.
https://forums.whirlpool.net.au/archive/2229505
I totally agree with you and the evidence is clear that Telstra have a major congestion issue at Peak Netflix viewing times. I have done heaps of tests and my regional ADSL service which is rock solid goes from 12Mb to >5MB at peak Netflix viewing times. The correlation is irrefutable.
Getting Telstra to admit there is a problme let alone do anything about it though will take a lot of patience and perserverence.