I have seen an old post saying we can BUT the post is pretty old so I wonder if that is actually true to this date.
I have only played DK and DH during legion and achieved getting a mount for those 2 classes, so with classes I have not touched at all during that time frame, can I go back at all and start a questline to obtain em or am I doomed for those other classes?
You can still get them.
Okay, andâŚhow/where do I start?
You have to complete the Legionfall Campagin (Broken Shores achievement).
Hereâs Wowheadâs guide for it.
Is it the one called âChampions of Legionfallâ ? and does it matter what character has the achievement?
Yes. Class mount progress is not account wide. You need to complete the Legionfall campaign and get the follower on each class. Even if your DK has the mount you still need to do it all again on your rogue, etc.
ShiiiitâŚThatâs alot of stuff to do all over again lol
Now next thing, its a been a while since Iâve done all this stuff so, is this all stuff solo-able? like there is no raids I have to do right to complete for my achievements that go toward my class mount progress?
Yeah itâs all nice and easy solo content. If you put your mind to it you could even get it all done in like 2-3 days
Awesome! Thank you to all of you guys answering my questions in detail 
Itâs called âbreaching the tombâ, âchampions of legionfallâ is only a part of it. You have to complete it on every class you want the mount for individually.
Yes and they are a lot of fun, except for waiting for table missions to complete.
In order to do them you have to also complete your Class campaigns as well.
If not you will hit a wall doing the Broken Isles/tomb campaign.
This will help a lot.
Is there any requirement of having to obtain the other spec artifact weapons? ie. Disc/holy for Priest? As I only play Shadow on my priest
Everything is soloable⌠however!
You do have to do multiple Mythic Dungeons along the way (they are different depending on class), and if your alt is suuuuper fresh (less than ilvl 300), you might have a hard time completing some of them depending on spec/class.
In any case, the best way to do it is with Wowhead opened.
MANY of the requirements have changed and made simpler, a prime example being you no longer need sentinax beacons to complete the marks questline.
If you plan accordingly, and know what youâre doing, breaching the tomb can be completed in a single day once youâve finished the class hall campaign.
What about this?
Pretty much you have to do all of the quests available. Some donât seem to matter but I havenât done the priest one yet, so I canât tell you which.