Last year, I was working on skill spreadsheets, similar to my Barbarian one, for all classes, however, I burned out from playing again and again, so I decided to quit altogether. Throughout the process I got some info from devs on skills where 100% calculations where impossible to achieve, Ranger Blessing being one of them. Since I won't be finishing full skill spreadsheets anymore, I might as well give correct info about this skill
Ranger Blessing: Player gets a chance to shoot an extra auto attack together with any damaging skill or an auto attack
Chance to proc: 10/14/17/20/25%
Duration: 10/12/14/16/18s
Mana cost: 15/17/19/21/23 points
Cooldown: 30s