I'd argue that the main navigation should be a static navbar that floats over the content. Rather than a scrollbar, a set of options (back, top, next page, etc) should always be accessible. With that, the scrollbar as it is should be fine.
Yeah. But that has to be a browser feature than something to be expected from page itself.
It would be nice if I could swipe from right end of screen and that scrollbar then allows me to fast scroll to some position.
On iOS, tapping the status bar will scroll the page to the top.