I have an iMac and a MacBook Pro under the same network connected through AFP file sharing protocol. Before I upgraded to OS X 10.10, the speed is very fast - copying a 200MB file would take a couple of seconds. Now as I have upgraded to 10.10, the speed slowed down drastically. When I copy a 200MB file it took me around 10 or 15 minutes. The iMac is connected to the router directly through Ethernet and the MacBook Pro is connected through wifi.
AFP is more so meant for a LAN configuration and not a WAN network. Instead you could try CIFS or another protocol and see if you see the same speed or an increase.
I would also try to use AirDrop and see how that works.