This quests did not show up in any of my garrisons untill i spent a day in Ashran. Not sure if i hit a certain number of honor points first, probably so.
I started getting these since the reset on 17th Feb., seems they're not new, as other comments here are from Patch 6.2... be interesting to know, officially, what triggers these.
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