Looks like there might be something in your facebook.net observation.
My environment:
Firefox 53.0.3
NoScript 5.0.6rc4
Scripts Allowed on theguardian.com.
Several pages have been hanging for me on theguardian.com, but many are live update pages so their content is probably too dynamic to be useful for diagnosis. However one of them is
https://www.theguardian.com/crosswords/cryptic/27218 which is unlikely to change over time (except visitor comments).
If I have scripts Allowed for facebook.net, that page hangs Firefox a few seconds after loading.
If I Forbid scripts from facebook.net (not even marking it as Untrusted), the page loads without hanging.
Perhaps not surprisingly, if I Forbid scripts from theguardian.com (and Allow from facebook.net), the page loads without hanging, but only as a static page.
For now I'll Forbid scripts from facebook.net as a workaround until this is fixed.
Cheers.