Not skill, experience. Now, EXPERIENCE can equal skill, so theoretically Grimiore = Experience = Skill, but not exactly. I wouldn't rely on it. Some people have a lot of experience and are still absolutely terrible. For them, experience is persistance, which, while being a good quality, is not what you're looking for if you're intending to speed run raids. So if we accept that experience CAN equal skill, enough it would be more appropriate to say that Grimiore = skill 50% of the time and Persistence the other 50% of the time. Which basically means it's a crap shoot and you're not helping yourself any.