The last game I played...
We literally could do nothing. Wraith was on top of us and moved around the map at great speed. We got stomped with 4 gens still pending to be repaired.
Also, SC doesn't work on wraith as long as it's cloaked. You only get the icon lightened up but you don't get the proximity sensor.

Comments
Proximity sensor is meant as a terror radius indicator.
Wraith cloaked = No terror radius.
it worked on no TR killers before 6.1.1