Ok, I could have been clearer in what I meant by that. I wasn't ignoring the fact that you mentioned other media, but you don't provide any examples of why you think mediums in fictional media support your idea that psychic blast should be the obvious choice for attack powers. Your examples mostly speak to real world mediums, specifically the stereotypes we tend to think of when calling to mind the various charlatans through history that have claimed to be able to channel the spirit world. Mediums in fictional media have displayed a wide variety of powers.
In the game The Medium, the protagonist, Marianne, can astrally project herself into the spirit world and manipulate spiritual energies to create shields or project destructive blasts.
In the TTRPG Geist: The Sin-Eaters, the players play characters who are bound to a ghostly entity and are able to see and speak to ghosts, allowing them to act as mediums. They can also manifest a host of powers that are all inspired by ghost stories from around the world: divination, possession, telekinesis, body horror inspired transformations, etc.
There are many examples in comic books and other works of literature of spiritual mediums who are also witches or wizards or other magical practitioners with incredible magical powers but no psychic leanings.
In movies like Ghost or The Sixth Sense, the medium characters have no powers or psychic capabilities outside the ability to interact with ghosts.
In modern culture, we tend to associate spiritual mediums with psychics because of our perception of real world examples, but fictional media, especially comic books which generally have a very loose relationship with what is possible in the real world, don't have to be bound to the idea of spiritual mediums being psychic. City of Heroes has plenty of psychic powersets already, I'd personally prefer it to be left out of a ghost channeling mastermind powerset.