So I'm no longer able to get the Feedback items anymore, and have been attempting to guess the legendary tier dishes without them. So far, I've been farming for about 5 hours, with no real progress to speak of. Since at Legendary tier the ingredient amounts vary by 7 (+/- 3), instead of 2 with the normal dishes, there are an insane amount of different combinations (~825.500). Even when comparing ingredients used with the grade a dish got (1/2/3 stars), it's still very hard to get an understanding of which ingredients are correct, since the grade seems to be based on how close you are to the correct numbers, instead of only on how many correct numbers you have.
On top of this, it takes way too much space in my inventory (after ~4hours of trying Burrito combinations, my inventory looked like this: )
And even after using all these items to cook dishes, it doesn't feel like I've gotten any closer to the actual combination.
Adding another way to get Feedback by adding the items to the shop would be a very nice addition and make this event doable for me again.
For all the dishes before the legendary tier, you'd need 1 Feedback item, and for the Legendary ones you'd need 6 per dish.
I'd say allowing us to buy 3-5 Feedback items/day would be reasonable (you can at most use 5/day anyways) and allow everyone to finish the event.
(Edit: Legendary tier ingredient amounts can vary uptill +3 aswell, instead of only going down to -3..... )