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The related system has only begun the beginnings of a start of a hint of an idea of balance and design.
Rarity serves a purpose in that it's fun to experience it, and more importantly, it serves the secondary purpose of specifically making newer players or newer Artisans have their porgression and dopamine feedback loops without utterly destroying the economy.
Basically, MMOs have a really simple problem. Every player wants to feel good and able to progress very basic things without devoting hours, but they also want an economy to work.
So you have, say 100 people who need to be able to get started and feel like they're doing something, but you also don't want 'enough resources available all the time for those 100 people to constantly want to do it, or to get burnt out of doing it'.
Enter the 10%.
Some games do it by making the combat really engaging and having the droprate be 10%. Some do it by having multiple gatherables that can come from one type of gathering point, and 10% of those are 'really important' and the others are designed to fall into natural personal consumption sinks. Throne and Liberty has recently tried putting the 10% on the output side with no real explanation, but in combination with the rest of their systems, it seems to be having mostly good effects.
If the designers are sticking with the 'common practice' of 'letting players trade 10% of what they personally interact with', then we need that Rarity system to be almost exactly as it is. They could fix some other things to make the pyramid work, and they've already started some of that, so we should probably just wait for them to finish it, before 'deciding to just scrap an unfinished system because it isn't fulfilling the feelings it is supposed to'.
It's not doing its job because it's not complete enough to do its job properly, so I say let 'em cook.