Well, there is a very distinct difference between controlling one of the energies incredibly well (Sepcarim) and controlling all three of the energies equally (Magestrava). Even the simplest acts of Outsorcery or Insorcery require the use of all three types of energy, and are thus only available to Magestrava. Monks, Sykers and Shamans each have their own unique capabilities, based on the energy they are bonded to, but they are also limited to them. They cannot cast magic from any of the branches at all.

EDIT: That being said, many Syker abilities can be emulated with Insorcery, Shamans control the same elements as elemental Outsorcerors, only better, and certain elements of necromancy and bodily-augmentation Outsorcery are encapsulated in the abilities of Monks.