If you can't make it so that all except .xml are ignored, you should also add the following to the ignore list: latencyTest.txt, latencyTest_v2.txt.
Also amongst the .xml's there are a few that you should ignore:
Bootstrap.xml (this one has been split into Bootstrap_2.xml and Bootstrap_3.xml), so there's no need for "Bootstrap.xml" anymore but it's kept around until all users have a chance to update Dash.
Drupal.xml (same as Bootstrap, it has been split into Drupal_7.xml and Drupal_8.xml)
Zend_Framework.xml (same as Bootstrap, it has been split into Zend_Framework_1.xml and Zend_Framework_2.xml)
Ruby_Installed_Gems.xml. This is an empty placeholder docset. Dash fills it with content at runtime (with the gems that the user has installed on his Mac)
Man_Pages.xml. This is an empty placeholder docset. Dash fills it with content at runtime (with the man pages that the user has installed on his Mac)
Regarding the ignore list at https://github.com/areina/helm-dash/blob/master/helm-dash.el#L99. You should change it so that anything that's not .xml is ignored, because I might add other .txt's and stuff in the future (although not that often).
If you can't make it so that all except .xml are ignored, you should also add the following to the ignore list: latencyTest.txt, latencyTest_v2.txt.
Also amongst the .xml's there are a few that you should ignore: