Some of the intermediary ISP's are erroneously flagging the transfers for a slower download (think it's torrent or other suspicious/low priority traffic). It's a bit detailed and may take some time to clear it up, but you could open Resource Monitor (resmon from run/search box) and expand the network/TCP section(s) to see what IP is being used for the download. Forget if it shows up as the launcher executable or not, but it should be identifiable in the list. Then you can investigate your connection issues with that particular server.

Testing connectivity via pingtest.net or speedguide.net is not giving you insight into your connection to the patch mirrors... it's just showing the quality of your connection to those particular test servers. Need to be looking at the specifics of your connection to the particular server you are downloading from... as that is where your problem is coming from, your actual path to the data source.

Once you know where you are downloading from, you can do a dig on the IP (whois lookup from a site like myip.ms) and run some tracerts to it so you know who is managing the traffic and thus who to contact to investigate things. For instance, if you are downloading from one of the Akamai mirrors, your ISP can actually enter into peering agreements with them directly if they don't already have a better established route to switch you too. But first, you will need to know more details about your connection that you can forward to your ISP to open a proper investigation into the problem.