I just had my moment when i got creative mind about how get something in WoW faster.
Now when all mounts are account wide, and you dont have all of them..
Basically, best for new accounts and for people who wants mounts fast´n quick rather than farming reputation with main races.
1) have any character with level 55+ for following step
2) create a DK, get out of the questing area
3) get to your city, buy yours race mounts...
4) repeat with other races......
IMO this way could be faster than farming reputation and with proper botting profile you can get the DK quests done faster than 1 hour.