i.e. go here, do that - get rare.
Push button - get rare.
Think it through, you're just repeating what I said. It absolutely has to rely on those things or it's not rare.
Well, when you put it that way it really sounds stupid - job well done for making me sound like an idiot.
BUT
To me rarity of a material should not depend on a chance of getting it through completely randomized process, because you can't look under the hood and see if whatever you're doing searching for it is right.
Instead, I would rather find this material myself. Scan systems in search for planet that has a better chance of having said material. Let's call it geologically-probable.
Then, once I locate it, scanning the surface to establish area of increased material's concentration.
Then search said area by means of low-altitude, high-speed flyovers looking for it visually.
Then, and only then, should I be presented with rocks that have a chance of giving me what I need.
See the difference? If not, short summary:
Currently, the system's spine
IS RNG, and it really makes it crap.
Whereas the way I see it a lot relies on player's patience and skill, which also increases with experience, then - and only then - should he be presented with RNG that should be SUPPORTING core mechanics, instead of being their backbone.
Sounds reasonable?