I get speeds very similar to Tweaker. I do regular system image backups using Acronis True Image 2010 to the MBWE. I’ve got a Linksys WRT610N router, connected using gigabit with cat5e cables. When the backup is made I get speeds in the 13 - 15 MB/s range (104 - 120 Mbps) very consistently. It takes about 90 minutes to capture a 75 GB system image. When the backup is done it verifies it. When reading back the file it takes about 1/2 the time and I get about 25 MB/s on the read.
When I use Windows Explorer to copy files to and from the WBME I get the same speeds - around 15 MB/s. Sometimes a bit higher, sometimes a bit lower. But I never get speeds as low as the OP has indicated.
Here’s an article, quoting WD’s own testing, that seems to verify the speeds I get are typical for the unit. http://www.tomsguide.com/us/westerndigital-mybook-worldedition,review-1200-8.html
I would say there is a problem somewhere in your set up.