Yes it used to be all JP servers were one DF grouping and all the NA/EU servers were all one DF grouping. But the release was a smashing success! and SE had to open new servers for both JP and NA/EU. This need to open new servers wouldn't work for their original DF grouping set up as the DF couldn't handled the load of the extra servers. So when they added the new servers they split the DF groupings into the groups that Sunarie linked.