Gnars Boomerang Throw only has 5 base damage at rank one.
Could it possibly Increase to 10 at rank one? considering it's a 10.5 second cooldown, 20 if you don't catch the return.
Inb4, It only does 55 damage from 115% Ad at level one for a base total of 60 damage, keep in mind most similar skillshots have either lower cooldown or 70+ total base damage at level 1.
I think 5 more damage is reasonable at rank one.