I HAVE THEM ALL
Is there any purpose in trying to run Campaign quests on more than one toon/covenant if you're already running it on Fae? I just learned about this last week and I'm at 11 Campaign quests on Fae and 2 on Necrolord, but to me it doesn't make sense to run them in two places if you get them all in one place anyway. Unless of course you fail at getting them?
Note that you have to have completed 16 campaign missions on one (your current?) covenant. The currency script shows how many campaign missions you have completed over all covenants, though. So if you're far beyond the 16 campaign missions and still not getting any mount missions that's probably the reason and you should just keep doing missions that add to the progress. Had to find out the hard way myself.