For people interested how to defeat the Adra Dragon with a ranger solo here's a little video.
https://youtu.be/ewxtIFixUb8
In the video I forgot to show my accuracy vs dragon defenses in the logs. My max accuracy was 126 with bow while the dragon's lowest deflection was 96. I had 100 accuracy when I used Binding Roots and the dragon had 100 reflex. With Scale Breaker and the debuff from Lenas Er the dragon had 119 fortitude.