I got all the Paragon mounts during Legion except for the Valarjar and Dreamweavers, by doing the Mission Table token farm mentioned above. I’ve been grinding them again non-stop since we got the rep buff, and got the Valarjar mount after only a few attempts.
I am now at 70 Dreamweaver Paragon chests and still don’t have the Wild Dreamrunner. Nor have I ever seen anyone riding it in-game. I’m convinced it doesn’t exist. The mount is a lie.
104 high mountain paragon chests, no elderhorn yet.
From what rariety says, the mount is supposed to be a 1 in 20 drop rate.
Now I know how RNG works, but 104 failed instances of a 1 in 20 drop is starting to get silly.
Obviously these mounts don’t have the reported bad luck protection on them.
1/20 is 5% chance, I don’t think it is accurate at all. Back them i felt like the drop chance was around 1%.
unless my math is failing (and it probably is) …stats on wowhead say that it’s around 1 in nearly 400
if you use the companion app, you can still run the missions for the tokens, then log in every once in a while to mail them.
What I did was had my army of alts (30) doing missions to get rep tokens, I had this toon (main a human) collect all the tokens and waited till darkmoon to get buff then turn tokens in, I would get min of 6-10 chests sometimes more 10-15. It is by far the best most efficient way to farm these.
On a side note it took me all of legion and 3/4 of BFA to get the last mount I need. 
Thing about wowhead is they get data from players, if players don’t share their data with wowhead that can lead to wrong % chances.
I know for a fact it took me more than 400 to get few of them, last one I needed was from stormheim and I farmed that all through legion and 3/4 way through BFA to get that mount, using 30 alts collect rep tokens.
that’s only way to get it, you do those training weekly and your chest will give you a quest item that starts the mission table to get fox mount.
Hmmmm 1 in 400 that just makes me sad.
The 1 in 20 value is coming from Rarity Addon. I have no idea if it is right or not.
I even asked Blizz support via a ticket. Apparently even Blizz support does not know drop rates. (interesting fact that).
Anyway… the farming continues.
Basically what I’ve been doing on all my alts. Farming tokens and using them on one toon.
The legion paragon caches are obnoxious and malicious design (imo). I think they need better drop rates or bad luck protection. They did retroactive bad luck protection for 8.3 rank 4 essences so I know they can do it.
It can take 100s of boxes to get 1 mount. That over a million reputation. It sucks that most have to farm them for years when they should have been buyable at exalted.
I want to farm the Valarjar mount but with limited time and hand pains I just can’t mindlessly do world quests every day for possibly years in old content. it’s bad enough that I have to for current content. I also missed playing Legion while it was current so I had to start late.
At least the SL caches seem a little better in drop rate for cosmetics.
They need to fix their mistake and either up the drop rates or put it on the vendor at exalted but they won’t because that’s not their style.