I went to Bolton with it in mind to try it. On the topo and in the description it climbs immediately left of Arch Druid, which was added later by John Hunt and could well be 7A. To be honest I couldn't see any holds on Mystical Powers and if it's a friction grovel I thought it would be too warm for it so didn't try. I also suspected that because of the blank nature of it there could be some hold share with Arch Druid. Add into that that I'm not sure how far back under the roof MP starts or whether you use the side wall etc and I just didn't try.
Rob did put a small bit of info on YG.com a while ago but I think it was a bit vague? Obviously this is now lost. I'd love to know where MP goes so I can heap suitable praise on Rob for his ascent. Perhaps if he was made aware of the vid then he can tell us where it goes in relation to AD? Is anyone in touch with him?