If at level 50 you're doing 500 damage and dragons have 10,000 Health, then at at level 81 dragons have 5 million health... that's what's repetitive and makes fighting a dragon a grind.
If I'm facing a dragon that has 50 additional armor, that means my attacks could do maybe 50 less damage. Do you know what options this opens up?
It allows me, the player, to now use tactics instead of just running up and repeatedly hitting L/R/L/R/L/R to just cut through their health.
It allows me to now go... huh, I have this Poison of Lower Armor that lasts for one hit. I'll use it to take a quick chunk out of the dragon and then maybe use some other tactics.
Quality of play > repetition of simply pressing L/R/L/R/L/R/L/R/L/R
Having enemies have access to other means of attack and defense also allows for challenge to be implemented.
A fight against a Dragon Priest would be a lot more challenging if he had a spell that allowed him to have an aura around him that disenchanted items for 30 seconds.
I'd still rather see more Thu'um variety in dragons though.
