New update on Urbosa's Fury.
It does 500 damage to Guardians and Lynels. I also tested on Hinoxes and multiple Stone Talus. There's definitely a large damage increase on overworld bosses. Given how I can't see how much HP Hinoxes and Talus enemies have, I can't give an accurate number. However since they are considered overworld bosses like Guardians or Lynels, I would say Urbosa's Fury does 500 to them as well.