I have an Asus RT-N16 with Tomato Firmware v1.28.9054 MIPSR2-beta K26 USB vpn3.6. I'm connected via cable from my PC, so wireless is not an issue.
I signed up for Astrill yesterday and installed the PC VPN client they offer just to test it out. My line is 20/2 and I've always gotten around 18/2 in reality. I expected it to be a lot slower on VPN, but to my surprise I tested it to 18/8(?) through the PC client (using speedtest and another local service). I retested numerous times, but these results were consistent throughout the day. I went through all the settings to make sure all communication went through VPN, and it did.
Today I decided to configure the router, and after a few hours I managed to get it up and working. The only problem is that the connection speed dropped to 10/2 consistently. Why would it be so much slower through the router compared to the PC client? I made sure the PC client was disconnected and shut down of course, and nothing else was running. I rebooted the router several times and even restarted my modem. So I'm wondering if my configuration is bad? Please have a look at my setup and see if I missed something. I didn't take a pic of the certificates, it's already working so they must be put in right. "USERNAME" and "PASSWORD" are of course dummy values :)