Here’s a check list

    • Turn Modem off for 10 – 20 seconds
    • Reduce the amount of connected devices
    • Turn Modem back on.
    • Check the network cable, if you have another cable, try that temporarily.
    • Turn the Firewall off.
    • Download + Install & Reboot computer. Leatrix Latency Fix
    • I know you said that you have updated drivers. Ensure your motherboard drivers are up to date, downloading drivers from the motherboard manufacturers website e.x. ASUS or MSI or ROG

    Don’t update drivers via Microsoft update, that is a no no, even Microsoft support techs advise not to do that, those drivers are more than likely unsigned and nine times out of ten will be out of date.

    If nothing above helps then call your Internet Service Provider tell them about the latency and connection issues that you are experiencing, they should do tests on their end and test your line.
    Another thing you can do is follow this article
    Follow their instructions.
    As far as guide pointing to wrong locations, can you please disclose which guide this is so that we can update it, Blizzard likes to make loads of changes to the game.
    I really hope that we find and fix this high latency issue, this sort of thing is really frustrating. I have been there a few times.