I thought it was odd that I was not seeing rolls for concealment against me after hitting level 8, and I confirmed with Radvul Stragat (Field of Ashes) that the 10% concealment isn't showing up in the combat log for him either. I do not know if this actually means it is not being rolled, or if this is some side effect of his Blind Fight, but I don't think it's working at all. I am still getting the Concealment buff icon at the top of my screen, and I reset my perk several times during testing.
Character: Volric Ashtallow
GSID: tacticool
May need to test this with someone who doesn't have blind fight, who gets to reroll to see if they hit, since you're looking at a 1%? chance he's going to miss. 1/(10^2)