For some reason, this mission wouldn't start for me. I put multiple followers in this mission, but every time I clicked to start it, it would go back to the list of missions, but this was still in the list and the mission didn't start.
Garrison Timer Mobile App
[Upon completion your 随从 will gain: ]
Missions and Followers math for maximising success chance
Warlords of Draenor Garrison Missions Guide