The Sitecore documentation that you linked to actually does apply to situations where you have multiple, dedicated Processing servers.

I think what you are getting confused by is the `singleInstance="true"` property of the `<history>` node, as seen below:

    <history type="Sitecore.Analytics.Data.MongoDb.ProcessingPool.MongoDbProcessingPool, 
      Sitecore.Analytics.MongoDb" singleInstance="true" >
      <param desc="connectionStringName">tracking.history</param>
      <Name>history</Name>
      <Enabled>true</Enabled>
    </history>

This property is actually not what you think: it is used to tell `Sitecore.Configuration.Factory` that when it creates the instance of the specified type, it should create the instance as a Singleton, and  thatall subsequent calls to create an instance of this type should use the existing Singleton instance.