I see it differently. Aragorn fought in wars for years and years. He has hung out with elves, spent time with dwarves, and fought alongside men. He fought off a group of Nazgul! And he is of different blood - literally, born different from others, being a Dunedain. In my view, LotR is a low level world, and he is at the top. Whether that means 17 out of 20, or 8 out of 10.
I'd go with the original D&D Ranger Lord and make Aragorn level 13 and the highest level human on the planet.