SunRazer
Back From The Dead
That's already been presented. The entire conversation with Valk's spirit goes unheard to Arcann and Senya. Once Valkorion actually produces a tangible physical effect (lifting the Outlander), the other two immediately notice and run up to him, but they can't do anything anyway.
Valkorion then goes into the Outlander's mind again, triggering that "time-stop" while he converses with the player in his head. The next we see of the "real world", Arcann and Senya are observing him on the throne in a trance, and they start fighting the droids that come in. Then it flashes back to the Outlander's mind. Clearly everything that happens with Valkorion in that instance was in the psyche, except for the telekinetic dominance which produced a tangible, physical effect and was therefore immediately noticed by Arcann and Senya.
Per his own word, Valkorion can't actually stop time, and if he could, the implication would be that as an entity he just entirely transcends time itself, which obviously isn't the case.