Even at Hokage old age I don't think Oro was a match for him considering he had to use the 1st and 2nd to get some kind of advantage and still came out of the battle which was for him a fate worst then death. Anyway aren't there 10kages total(5 great villages/5 small villages) but only 4 that we know of(Hokage, Kazekage,Mizukage,Oro). I remember the map showing 10symbols.