While the idea of giving players rewards for accumulating reputation with a faction after the exalted status has been reached is perfectly reasonable, I would argue that mounts and pets should not be RNG drops from paragon caches. Such items, if they must be put in these loot boxes at all, should be 100% drops.
During Legion, I reached appalling numbers to get all five such mounts from the original factions. Here are my approximate numbers (I was running my main and two alts – I did very few WQs for these different factions once I got the mounts, but I did open a few more boxes after I got them):
Court of Farondis – 66
Dreamweavers – 80
Highmountain Tribe – 73
The Nightfallen – 79
Valarjar – 43
Afterwards, these mounts continued to appear in later Legion patches, in BFA, and now, in Shadowlands. Thankfully, the drop rates are much better than they were at the beginning of Legion, but still not 100%. For instance, it took me seven Mysterious Gift from Ve’nari to get the Soulbound Gloomcharger’s Reins, and today, I did not obtain the Tamed Mauler Harness from my second Supplies of the Archivists’ Codex. I am dedicated mount collector, but this latest failure felt particularly awful. Considering the renown-based time-gating system to upgrade Korthia catch-up gear to 226 and 233, it is unclear why the reputation given by Korthian relics is half of their nominal value. Moreover, the grind for the relics is long, repetitive, and boring when done continuously for months. Actually, it sometimes feels like the existence of paragon caches constitute a behavioral science experience on operant conditioning to see how many repetitive behaviors a player can produce without reinforcement. Perhaps Blizzard has data that shows that it works, but I am pretty sure that BF Skinner never asked his rats if they were enjoying what they were doing. Grinding RNG paragon mounts in not a fun mechanic.
Finally, in anticipation of different comments that may appear, I do not feel entitled to anything. You can view my profile – I am perfectly fine with the concept of earning rewards in game. Next, sure, some mounts can be “rare” or “prestigious”, but that has nothing to do with the pleasure derived from trying to acquire them. Finally, I know, “I don’t have to do it”, but that argument is simply poor. One does not have to collect mounts or anything else in game, or raid, or run dungeons, or PVP, or play World of Warcraft. There are many in-game mechanics to earn mounts that are quite fun, but RNG paragon cache mounts are not one of them.