Thanks for this thread. I didn't even notice till I saw this. Was on Sierra Safari 10 and iOS 11, and was just as you described.No, unfortunelty Safari 11 does not fix iCloud tabs in El Capitan.
It is frustrating that such a simple feature is deliberately broken and the fix is withheld from El Capitan despite Safari 11 being released. I too will have to live without iCloud tabs.
Upgraded to Sierra Safari 11, and iOS tabs are showing up now. But.. doesn't update all that quick (have to close a iOS tab through Sierra for Sierra to update the current iOS Safari tabs.) Will probably sort itself out later like iCloud sometimes does.