Wembley808: This is really stupid... less than 1mb per sec... it's going to cost me in electricity more than the games worth... no real way to cancel on this STUPID SHIT,, sorry SITE..
I just started downloading The Witcher 3 with Firefox. It is coming at full speed to me right now, which in my case means 10 Mbit/s. So at least the speed problem you are seeing is not universal.
Not sure whether you are trying to download it with the Galaxy client, or the offline installer with the web browser. At least the latter option works fast for me. If you are in a hurry, you might consider downloading the game with your web browser instead, install it, and then import the installed game to Galaxy (if you want to play it through Galaxy, and not without).
Downloading it with the web browser is probably a faster option anyway, as the offline installer files are compressed, while the Galaxy client probably downloads the data uncompressed (meaning much more data to download).