Everything works this time actually, it got fixed with past maintenance. Quest item percentage bonus works for all the quest.
For example the item for valeria vendetta normally is 50% drop chance, now is 100%:

https://imgur.com/a/d4EjrK5

And about the scenario buff, i will use rose spirit quest as example. This is before entering quest mission to battle her: 71 dr
https://imgur.com/a/zp1uOBP

And during battle: 74 dr
https://imgur.com/a/yiPKRGU

Kind of salty because i had to use warp free item last weekend to hurry on quest, because it was not working, but it was an event one for 3 days anyway.
Edit: warp free works now too, it asks to pay 0 feso