I have just finished the legion warlock order hall campaign, unlocking the “heroic weapons” and it was my understanding that i would get a transmog for the artifacts. In fact, I saw an animation showing the new aspect.
However, once i tried to actually transmog it… nothing? It’s not in my collection of available transmogs.
I know that some appearances were removed - like the Mage Tower and… eh… +15 Mythic? (please correct me if I’m wrong).
(Edit: I stand corrected. You can still obtain +15 appearances, see links below)
“Heroic Weapons” should not be amongst those to my knowledge. Especially seeing as you are still able to obtain them, so they shouldn’t be restricted to anything other than weapon type at the most.
When you unlock a new look for your weapon it’s always required to fully relog the game for it to show up on your transmog options. No idea why, but it’s been like that for a long time now.
Mage tower appearance is indeed unobtainable but I think you can still earn the +15 ones if you do a BfA +15. At least they said you would be able to still get it.
The system that adds artifact transmog to your collection scans your unlocked artifact weapons only when you log in. That’s why right after unlocking new appearance you don’t get it in your collection. That’s why you need to relog so the system can find new unlocked appearances and add them to your transmog collection.
If you use the artifact forge to change the actual artifact on that specific character, yes, that is instant.
Getting them to the transmog collection and having it account-wide for appropriate class is not and a relog is needed.