Would using Ghostery be necessary in the Tor web browser? I know that my IP would be unknown but my patterns are well documented. My Tor browser settings are set to high.
Generally all extensions are bad. If they affect how the browser behaves they are fingerprintable and therefor reduce your anonymity because your browser no longer acts like other peoples.
Firstly, most of these addons work by blacklisting which is always insufficient and flawed. Infact a study of such addons found there were cases that it always missed and that it always missed new, emerging fingerprinting techniques. This means that rather than improving your privacy, in the case of Tor Browser they are harming it. To get privacy on Tor Browser use 'New Identity', it will protect you better than any addon.
Secondly, Ghostery is proprietary software. There is no source code available, you will not be able to tell what it is doing without some reverse engineering effort.
Thirdly, Ghostery sells you information to advertising companies, presumably the very thing you were intending to avoid.
So you should not be using Ghostery. If you want to block ads, use an adblocker but don't think that addons will stop tracking, they absolutely will not. At best they reduce it, in many cases they will make it worse.
It's a good thing to have, so the answer is YES: the neccessity of using Ghostery is not eliminated by using non-direct TCP transport(i.e. using Tor instead of direct clearnet) - it does not change the end point, the website you're visiting. And - it's not eliminating tracking scripts like Google Analytics. So Ghostery is must-have thing. Also consider using a Perspectives Project to verify HTTPS certificates, a good thing to have.