I sympathize.

For those who don't mind, or prefer, a less comprehensive vim experience in the browser, I'm very happy with VimFx https://addons.mozilla.org/en-US/firefox/addon/vimfx/

It has a ton of vim commands, but I only use hjkl, g and gg. I never can remember whether search with / comes via VimFx or plain FF.

Firefox says it's compatible with multiprocess, but I don't know if it will survive through the switch to WebExtensions. It works fine now.