Files under https://performance.wikimedia.beta.wmflabs.org/xhgui should definitely be disallowed. When I was testing the new XHGui today I noticed a lot of crawler traffic hitting old profile IDs.
Files under https://performance.wikimedia.org/xhgui should probably be disallowed, too, unless there's something I'm missing.
Arguably, we should disallow everything on the beta site, as there's no reason for crawlers to be hitting it instead of the main site. To do so, we'd need a mechanism for serving a different robots.txt based on realm, e.g. an alias in the httpd configuration.