Beer man,
I think we could define a sandbag in the sense of inactive, low level accounts that do not contribute in any way to the war. If you have global age players with low level defenses and maxed offenses, then you are simply a liability for your team, and not a sand bag. As an active Enlightenment age base, i have beaten many opponents in WW that are Global or Atomic with extremely limited defenses. So, while that player may be able to attack higher, they are also beaten by much lower level players, and therefore it is a bit of a wash.