Is it possible to have my dock visible on all monitors in El Capitan?
After extensive search, I have not found any solution specifically for the native macOS Dock.

However, not wanting to put up with this nuisance, I configured the third party Contexts app to always be visible and show only icons when not hovered.

I'm more than happy with this solution. The only drawback is that you cannot configure the context sidebar to be in the bottom of the display, like the dock.

Disclaimer: I'm not affiliated with this app in any way.