Primus has a 12 wis, giving +1. He’s proficient in Perception, giving +3. That’s a +4 to normal Perception rolls. And he has the Observant feat, giving +5 to passive. That’s +9 altogether. And Passive Perception is 10 + any Perception bonuses. So...19.
He can have Darkvision when he’s Focusing on his Third Eye Discipline. He can also use Power Points to get tremor sense, X-ray vision or true sight.
The new Psion class that they are working on pretty much did away with the entire Mystic class structure. Once they come out with a workable version, I’ll be changing him, so who knows what he’ll be able to do at that point. But for now, he’s the best parts of all the Genasi siblings.