Swami Sivananda Radha used to meet her guru, Swami Sivananda in her dreams for many years, both before she had ever met him, and afterwards. In these dreams he called her attention to the spiritual work that she needed to do, and after they had met but were separated geographically, he continued to provide guidance through his presence in her dreams. I think that this is very real guidance. If you think of the guru as a divine presence, and one that is deeply connected to your own higher self, then it makes perfect sense that your "guru" would connect with you through your dreams.