How can I change the  on a View filtered by NID so that it is the referenced Node's Title field?
You need to "Specify validation criteria" in your contextual filter.

In your Contextual filter scroll down and check the box "Override title" but leave the text box empty.

Next, check the box "Specify validation criteria" and select "PHP Code" from the validator menu.

In the code box enter the following:

if($argument) { // Check that argument is present
    $myNode = node_load($argument); // Load node based on NID
    $myTitle = $myNode -&gt;title; // Parse node data to get title
    $handler-&gt;options['title'] = $myTitle; // Change the view's page title to node's title
}
return true;