would you advise that No Script in Firefox is somewhat redundant and could be removed.
It isn't redundant as it isn't doing exactly the same thing, avast is scanning scripts present on that page. NoScript blocks all scripts on a page unless you specifically allow that page to run scripts. NoScript also has cross site script blocking by default.
In the event of avast not finding anything wrong in a particular script, NoScript would stil block it until you specifically allowed scripts on that page; this is handy in the case of a false negative (no detection), which would allow a script to run.
No single AV solution is going to catch absolutely everything in all areas, which is why a layered approach to security is advisable.
