You would indeed think they'd have learned, from other MMOs. This was figured out by Blizzard at least four years ago: download most of the new stuff beforehand, in the background. "Exceptionally high demand" -- no %@$&, Sherlock. If you make everyone download the new stuff at once, that will happen.
At LEAST when you're stuck in the queue for patch servers or authentication servers, put up the number of people ahead of you. Again, Blizzard did that years ago.
On the positive side, I did not run into a corrupted file problem (at least I don't think I did, as I got to the authentication stage). Just about 5 hours trying to patch, and now several more trying to authenticate.
What a bunch of @$$^&#%&*.