I have made a new Dwarf character because I wanted to level through their starting area and beyond also hoping to unlock some missing transmog pieces. I was under the impression that as of 11.0 once you complete a quest you will unlock all available transmog, even the items that your character can not equip.
However I have noticed that this is not the case while questing through the old world. Is this intended, did I maybe misunderstand how unlocking transmog works?
I didn’t see anything about the quest rewards mechanic being changed in the notes. From what I understand, ever since transmog was a thing when you completed a quest, you’d get all the item mogs for the things your character could choose from the rewards.
If there were mail shoulders, chest and pants to choose from and you picked the shoulders, you’d also get the mail chest and pants mog. I don’t think doing a quest on one character will give you items that might be given to other classes / armor types to pick.
I’d really love for that to be the case to be honest, it’d be a great time saver to just run through all campaigns on one character and unlock each and every transmog that quests would offer. However - since the game is about engagement numbers, I think Blizzard dangling the carrot being able to learn mogs from boss drops of another armor type than your own will push that engagement since mog farming got more efficient.
I don’t know if it’s not been implemented or they changed their minds, or it was bugged before or it’s bugged now
I’m afraid that this is incorrect, and was most likely a bug during the beta. Sorry.
Update: New information has been shared by the World of Warcraft development team here: Collecting Appearances in The War Within
That is enormously disappointing. I was extremely excited to do a Loremaster and gain all the quest reward mogs this way. I feel very deflated now.
That’s understandable. 
I would definitely suggest sending feedback to our developers about this, this sort of thing could always change in the future:
It seems Morgan Day said a couple of months ago in an interview with MrGM that not only quests were gonna give all the rewards, but also that it was gonna be retroactive…
This feature and warbands were the things that I had been looking forward to the most for this expansion. Don’t want to do Loremaster 4 times to unlock all mogs (or even 8 times, as some mogs in BC are faction-locked)
It was indeed said during an interview by Morgan Day that all armour type appearance rewards from quests (as they were behaving on the Beta) will be retroactive. Specifically this interview (timestamped).
Bravo Blizzard, you absolute clowns
Perhaps it is merely coming in TWW release and not the pre-patch, and this has not been communicated well to other parts of the Blizz team.
Could we get any kind of official confirmation? GM says one things, but Morgan Day and Wowhead say the opposite.
If only those code wizards over at Blizzard HQ could pry themselves away from their dollar-stuffed Big Macs long enough to glance at the EU forums once in a while…
Can someone who can comment on the US forums let people know about this?
This is the respective US post that has way more traction and no blue answers whatsoever:
This is really disappointing
“Unfortunately we created a good thing that everyone liked. It is now been fixed and removed. Have a bad day.”
oh fun police detected…
this is really disappointing, especially when this feature was known for a long time and only now they say it’s a bug?
It feels like they are just making fun of us.
BOOOOOOOOOOOOOOOOO!
(This part is just here to make a complete sentence because blizzard doesn’t allow me to just type booo for some reason. Please ignore this)
This is very disappointing. On an expansion where the main selling point is “respecting player’s time”, this is the one thing that will probably put me off the game for good. All these years I was hoping to not have to repeat all these old quests up to 8 times, and now we have a confirmation that it’s not gonna happen.
Regarding comments on wowhead post (https://www.wowhead.com/news/blizzard-confirms-quests-will-not-reward-all-appearances-in-the-war-within-345742?page=8#comments) no one is happy with this revert/bugfix.
Loremaster is one of the longest achievement ever, and no one will like to do quests from 4 to 8 times on an account. Collection is a thing, but no one will do 500k quests for collections.
It’s totally disappointing that the multi armor collection feature was one of the most awaited by collectors with the warband system. We have almost fully it on dungeons. Please just tell us that you will reconsider and fix it in the 11.0.5 patch in 3 months and that’s all
Hey all,
Just to clarify a couple of things, before closing this thread:
Customer support is not involved with the development of the game: I can only confirm that what has been reported by the OP is not a bug.
Our team will often post on these forums to provide more information on different issues that you all encounter, such as confirming that there is currently a bug with several achievements, that a quest doesn’t appear to be progressing, or that a title is not being granted, for example. Alternatively, we do have many support articles on the support site to provide more information on specific issues, such as this one (PVP Bar Doesn’t Fill Up - in this case, the issue is not a bug but can sometimes create some confusion, and tickets).
As always, if you would like to share your feedback about how something works in-game, you can create a thread in the General section of this forum or share it in-game, for example. Alternatively, you can also post on Twitter, Reddit, or the social media platform of your choice. 
Thank you all for your understanding.