Get to Fort Faroth. Get a rapier with bloody slash ashe of war.
Get naked (as light weight as possible) and stay mounted, Get on the little rock formation and start hitting the dragon.

After 20+ hits there will be a bleed chunk of 13k, so once the dragon is down to less than 10 percent of its health, go slower. You want to make sure you have atleast 50% stamina. The moment you see the dragon tail wiggle, rush back to the site of grace ASAP, jump down and grab it before the dragon "dies".

Still works in 1.10.