I transfer a 5200MB's file, by SCP, between to servers on my LAN in 8:36 (84.5Kbps). Is that a good throughput?
You might want to make sure compression is turned off when using SCP just in case there's a CPU bottleneck (could be disabled by default though), make the destination file /dev/null, use dd with /dev/zero as the source piped over ssh and... ah might as well use iperf?
Not sure about your maths there though, 5200MB in 8m36s seems more like 10MBps than 84.5Kbps...
3413MB in 3m27: 16MBps from cheap Dell laptop to local dev server's motherboard LAN port via Asus RT-AC66U switch - your servers must really suck if they are slower than that!!