So, I am not sure if anything has changed I am only finding old info but I would like to work on my class mount for my warrior however I was curious if you still had to do the breaching the tomb meta achievement on each class you are trying to get the mount on. Thank you in advance!
This was changed in the latest patch to be account-wide once completed on one character. I haven’t done it myself yet to see if there are any issues. From the patch notes:
- Players now only need to complete the achievement Breaching the Tomb on one character per account to begin the Legion class mount quests on the Broken Shore. Each character must still complete their class hall campaign, complete quests, and recruit their final order hall champion.
Awesome, we will find out soon enough if it works haha, I am just about to that point 
Good luck! Report back with any findings 
Alrighty, update… So. I completed the entirety of the campaign, got all the achievements for it however the Valarjar Warsinger is not at the Broken Shore like he is supposed to be. I have tried a ton of recommended things like clearing files and disabling addons with no success. What am I missing here?
Edit: It seems to work okay, I missed something. Make sure after the campaign you go to Khadgar in the tower and complete the “Uniting the Isles” quest he gives you. Then you will need to go to the flight pad in Dalaran and talk to Khadgar there again, get the Broken Shore questline and finish it (just the orange quests he gives you that leads to the violet parlor). That has to be done before you can even see the Valarjar Warsinger at Deliverance Point.
You do not have to continue the Artifact weapon quests once it gets to that point. Go back to Deliverance Point, pick up Champions of Legionfall from the Warden and start your final champion quest. At that point you should be able to accept the mount quests
Also as a heads up you so choose to do the Artifact quests, mind you some of the mobs are scaled incorrectly up to level 60 so don’t do it on lower alts xD
So do you need to do the artifact quests in order to get the class mounts? This is where I am now - dealing with the level 60 elites. I think I am on the last one (her brother) and I just cannot kill him.
Yours is different from mine. But you have to complete the entire class campaign, then only the first part of the artifact quest that Khadgar gives you after uniting the isles. After that go talk to him at Krasus’ landing and you should be good from there.