Is it me or is it limited to a download speed of ~400kb/s

My normal download speed is around 7MB/s (not Mb)...

Flo that is due server connection to you, since SS was patching at the same time it will vary from user to user, purely because your downloading it from the server and the server connection speed may differ from your house

the patch server is on a 100mbit connection (unlike the game server which is on an 1gbit connection for minimum latency). so yes, when everyone download the patch at the same time, it can get a bit slow on the bandwith. (full install is not hosted on our server for similar reason). Since patches are generally pretty small to download, its not exactly a big deal most of the time.

There is a plan in place to quickly switch it over to the 1gbit network if we ever need (at the cost of making the game server spike a bit when people download). but right now the speed is sufficient to not be problematic on patch.