RNG, unfortunately, has been applied to almost every aspect of this game. At least the beast tribe minions and mounts are a rep grind which is fine and expected. Dungeon drop RNG is also expected although skewed a lot of times. There are things that I simply will not attempt due to the RNG factor.
I have done none piesteskin maps daily for almost a year and not one minion, or blue fox hide or rush grass. My novus will likely never be finished to my stat satisfaction due to the RNG of first getting useable materia and then affixing said materia, all based on RNG. This is notwithstanding the horrendous ATMA RNG grind to get to the Animus in the first place.
Desynth is something I started but won't finish due to RNG. Of all the primal runs, I have only seen the mount from Levi Ex once, nothing ever from the other primals. If anything makes me stop playing this game, it will be the heavy reliance on RNG for everything. A certain amount of grind I can handle, but heavy grind plus heavy RNG grates on the nerves after a while.