The scrolls for tempering you can get in hordes, I have about 40 just from infernal hordes. Elixirs and incense are almost all only better then the other ones if you are in a party… and that’s the point. Solo players who don’t want to do party play (me) don’t benefit from these consumables (except the move speed one, but move speed is capped at 200% which is easily reachable without it).
So the only actual claim is it offers the best gear in the game… this is just untrue, there is no gear exclusive to the citadel and I would put money on grinding other end game content is probably better.
So yes it offers cosmetics, but I couldn’t give a monkey’s about that as its no advantage ingame.