Too be honest i don´t think there is a problem with RNG or that they changed any rate. Actually i can speak from experience of the 2021 Event where they still had Steelrose on the list of available Dungeons for the event. From maybe 90-100 runs i concluded that the droprate of temperings was around 1/10. This was without lootbufs nor weekend buff. It is not even safe that these buffs work on event droprates or if they are a fix value. Anyways does that mean if you get nothing out of 10 or maybe even 20 runs that you can have simply bad luck.
I think the major issues is that they consistently nerfed events over the years what actually cause a lot of the excitement by players to fade away, cause these events were always aticipated for many months. Compared to the first events in 2020 Steel rose has been removed for the icepicks and temperings and from what i remember also that the amounts of Ice pick chest had been reduced. Then also The upper Udas Boss has been changed from the Nexus to anurati which takes way longer and is a lot more difficult to kill.
I think these changes combined now with the much shorter time of the event causes a lot of disapointment for many players. Ofc it is also not in the interest of the server too cause a deflation of the value of Event Wings or Temperings, but i think personally that it´s never a good decision to take something away from players which others had already a long time the possibility to exploit.