Honestly you can do whatever you think makes sense.
As the table illustrates, you can't make everybody play a divisional rival twice because we don't have an even # of teams in the division.
Ex., Team E has to play F (different division) as their second double-up.
If we wanted to force E to play A, B, or C as their second double-up, then A, B, or C would be playing a divisional rival for three double ups AND they would have to not play a specific team in the league that year.
Am I wrong about that? Maybe I am. I don't know.
So Yahoo seems to optimize it automatically now. Just not between years.