Batch logic can lead to unbalanced use of system.batches

 if (validated.size() - validated.get(localRack).size() >= 2)
 {
        // we have enough endpoints in other racks
        validated.removeAll(localRack);
  }

 if (validated.keySet().size() == 1)
 {
       // we have only 1 `other` rack
       Collection otherRack = Iterables.getOnlyElement(validated.asMap().values());
       
        return Lists.newArrayList(Iterables.limit(otherRack, 2));
 }