Lots of people have wanted to make Manson something/ somehow*more* than just a pyschopathic, manipulative, drugged-up, charismatic, occasionally disarming murderer. Whether they invest something mystical in his ramblings or, as in this case,suggest he was part of some mysterious 'bigger picture'. He's good copy. However, I think you'll find the truth is that he was indeed a pyschopathic, manipulative, drugged-up, charismatic, occasionally disarming murderer. Sharon Tate was just one of the victims of the Family. High profile, photogenic, more good copy. The Family most likely chose that house on Cielo Drive that night because it had been owned by Terry Melcher, who had crossed Manson in the music industry (he was, of all things, Doris Day's son!). That, plus the other Family murders, the trial proceedings and subsequent investigations: all suggest strongly that there was no 'someone big' planning to klill Tate.
I can't think of a book or writer linking Manson and Hess, (unless some freak has published witterings linking them with Martian invasions and crop-circles or the like!). The best book on Manson is, I reckon still, Vincent Bugliosi's Helter Skelter. (Bugliosi was the prosecuting attorney).