There is no evidence of drop rate nerfs, but the loot table itself is visible to everyone and in nearly patch nerfed compared to KR.
Celestial Basin f.e. KR gets Hongmoon Master Scrolls and Pet Collections, EU/NA had them removed
Chaos Supply Chain f.e. KR is getting Square+Penta+Hexa Gems (~30% each), EU/NA has Square+Penta only (~50% each). Same applies to Pet Gems, KR has Octa+Triangular+Square Pet Gems, EU/NA has only Octa+Triangular
Same with Transmutes, EU/NA requires the additional item "Challenger Token", in KR you require a few tradable materials (Soulstones, etc but not many) to fuse them.
Same with Unity Stones, KR has no awakened legendary stage, we have one full additional stage to make it more grindy.
EU/NA also requires 5x more Synthesis stones compared to KR, while not having any gold sources (like the daily changes or Kaebi village in KR).
Soul Boost also has nerfed rewards compared to KR.
We didn't get any positive changes, only changes to make it more grindy, more p2w, so of course I'm kinda tilted, especially with the patch we got this month, since they legit removed ALL the useful content you could get from there. There is literally nothing left to farm in Celestial Basin (and even more skins got removed and are now forever unavailable in the game).
Don't take me wrong, I'm not criticizing Green Storm, I'm actually really glad with how he interacts with the community, he just had the bad luck to get thrown into this dumpster fire. I'm purely criticizing the people making the decisions to just nerf every single patch EU/NA is getting. It feels like in every patch they go over the loot table and just cut the best rewards you could get.
I would be so glad if we could just get everything KR gets 1:1, I don't even mind if they include every single bug KR got (I mean we are getting them currently already anyways).