We've created a pretty basic Umbraco 7 site for our client and they are trying to install it on 3 web servers sitting behind a load balancer. We've tried to follow this guide as closely as possible: http://our.umbraco.org/documentation/Installation/load-balancing

They have dedicated one of the web servers for the backend office editing and they have made the following changes to umbracoSettings.config file:

<distributedCall enable="True">    
    <user>0</user>
    <servers>
      <server>10.11.7.11</server>
      <server>10.11.7.12</server>
      <server>10.11.7.13</server>
    </servers>
  </distributedCall>

When a change is made in the CMS and published, the changes are not reflected on the other two servers, indicating that the cache syncing is not working. They do have DFS Replication working and have set it up to ignore the App_Data folder. Should they have the server that is being used as the Backoffice editor in the list of servers?  Does anyone have any suggestions, resources or tricks as to how and what to troubleshoot? Thank you in advance for any help.