I haven't measured it, so this is somewhat subjective but yes, I could see a noticeable (although very small - nowhere near ~6 seconds) speed-up after disabling

I haven't measured it, so this is somewhat subjective but yes, I could see a noticeable (although very small - nowhere near ~6 seconds) speed-up after disabling HTTPS Everywhere. In addition it was the most memory hungry of my addons (although I don't use much, just it, NoScript, uBlock Origin, Canvas Blocker, and VideoDownloadHelper), taking about ~12 Mb, as reported by Firefox. Also a significant number of sites broke for me, and disabling the rule for that site would fix the issue. I think it's showing its age, and besides it's becoming less useful in an increasingly https centric Web. Am hoping the rewrite/refactoring necessary for migration to WebExtensions can help improve its performance too.