Updating the standalone client is super slow / checking files takes 3 hours

I uninstalled the game a while ago and now re-installed it and the download speed is extremely low.
I have wildly fluctuating speeds for PoE patch updates, sometimes as low as 145KB/s. Very briefly it hit 3MB/s but most of the time it's between 150KB/s and 500KB/s.

I am not downloading anything else at the moment.
I am using Windows 7 Home Premium and made an exception for PathOfExile.exe in my firewall (in and outbound) and in my antivirus program (including behavior shield and fiel shield).
My Max download speed is 50,000Mb/s and everything else can make use of this (torrents, browser downloads not capped server side, etc.).
Nonetheless

Besides that checking existing patch files also can take upwards of 3 hours.
A week ago I tried to install the game again and after downloading 1-2 GB I turned off the update download, then later I turned it back on and left it running while doing some other stuff (not downloading anything else) and when I checked back the update was still check my existing files after more than 3 hours had passed.

At the time I stopped the download and uninstalled PoE, then checked that now folders are left (e.g. the GGG subdirectory under Programs).
So this is an almost clean install, I haven't checked if any registry keys are left from the previous installation.

PS: allocating space usually only takes a few minutes.

PPS: Using Steam is not possible because the Steam client disconnects a lot whereas the standalone client only disconnects occasionally.