it seems like there has been a change to the way garrison missions are spawning and no confirmation by Blizzard at all that this is "working as intended". I have 2 100s with all 25 of my followers maxed at 675 and with character Ilvls in the 660s and for weeks I would get my standard daily 675 missions for Apexis, resources and gold. Every once in a while I would get a "Rare" Burning Blade mission that would include the follower retraining items but none of the new rare missions ever popped up. I chalked it up to bad RNG and went on my way.
I have a level 100 shaman (Ilvl 635) on BH that I was able to get 7 of my followers to 675 after 6.2 went live. Now outside of my initial 645 High Maul mission I have not seen a single mission over 630 since. Before the last patch you would get your BRF 660 mission once three of your followers hit 660. That has not happened for my shaman. As I stated earlier not ONE single mission over 630 yet and it's been weeks. That's not RNG as you should be getting missions daily at 600, 615, 630, 645, 660 and 675 (does not always mean rare) if you meet the previous 3 followers at (x) follower lvl requirement. While only 7 of my 25 followers are at 675 the other 18 are resting between 615 and 660s. I definitely should be getting missions higher than 630 daily.
So, I checked the forums and saw a thread about character Ilvl and the new 675 rare missions. I tried on my hunter first. Got her to Ilvl 675 and immediately got the 675 Rare mission for that dog companion pet. Tried it on my priest next and I did it while at my mission table. Got her to Ilvl 675 and immediately got the 675 Rare Bulging Oil Barrel quest. These new 675 rare quests all share the same lockout so while you might be looking for the void trinket there's also a gron mount, an elixir that boosts XP gain, rep gain token, etc. and they appear to be on a weekly cooldown.
Also, it seems like it's not your equipped Ilvl that counts, but your total Ilvl. So, if you have equppable gear sitting in your bags that for some reason (subpar stats or not BiS) is not equipped the new rare missions will still pop. Tested that on my priest.
If you haven't got a single new "Rare" mission yet despite having maxed out garrison followers try getting your character Ilvl to 675 and see what happens. It couldn't hurt and its relatively easy with Apexis epics. Maybe Blizzard is just trying to make sure we leave our garrisons now.
Ashley