There should always be the fine balance between what is essential added layered protection and what is just harmful "overkill".
So you should know where your AV is performing "under par", so to say. So do not add more of the same there, because that is no solution. Here for instance users could be glad to have Adguard as an extension inside the browser as AOS does not flag - an example:
Adguard has blocked access to this page
This web page at wXw.poddebice.net.pl has been reported as a phishing page and has been blocked based on your security preferences.
Adguard has found that this page may be a forgery or imitation of another website, designed to trick users into sharing personal or financial information. Entering any personal information on this page may result in identity theft or other abuse.
Sometimes I have DrWeb's extension flag issues Avast misses, sometimes I am warned by "informed"WOT user reports for AOS omissions.
And here I only touch in-browser detection as that is the special terrain I happen to have gained some relevant knowledge. So I know about the blind spots of Avast detection there so I have put up some extra "rearview mirrors" to be better protected, and also report these "blind spots" to Avast as almost on a daily basis.
polonus