I take issue in your tone. Why are you being to aggressive? Also, (surprise!) I disagree with your opinion.
Skarner's rework (it's not supposed to be a nerf) was absolutely unneeded. He was unplayed, not very strong, and niche. Riot took him, butchered him then sewed him back together. His play rate was low, and now it's... still low. Win rate, low. Good job, riot! I agree that they won't undo his rework though.
The problem is that all the old players of Skarner unanimously agree that his current version is vastly underpowered. And it's not even Poppy or Urgot-levels of niche power, but no power at all.
Disclaimer: I don't play Skarner.
Kayle didn't really need the nerf. It was Lich Bane that made the Q so oppressively strong, and now with Lich Bane going away she's mediocre. Unlike Fizz or TF, she didn't even get a buff to compensate. The extra movement speed on W is nice, and so is the 0 mana cost, but going by her play rate she wasn't really toxic per se.
Xerath's rework isn't that great. Sure, he feels more fluid, but a lot of his identity was lost (hey look at me I'm charging my long range skill shot! Before it was super-long-range skill shots, like artillery with long durations between shots). I think it'd be a 50/50 split on this one.
Why would Karma players cry about the (new?) Karma? She's an excellent mid/top/support. It's just that she completely lost her old identity. She hasn't had any buffs nor nerfs in forever, too.
Disclaimer: I am a New-Karma player.
Urgot is pretty fun to play, but he's also soooo immobile ;_; Plus, his ult seems rather bad in a 1v1 situation like Top lane.
I'm aggressive mostly because I'm tired of people bitching about nerfs as if it'll change anything. The community is negative enough as it is, there is absolutely no reason to be spreading it.
Skarner's rework was massively necessary. He needed to be able to be buffed, and his permaslow was bullshit. While the fantasy of "I get into range of you, you never escape it" is one that isn't satisfied, it won't ever because the entire concept of it is that there's nothing the target can do about it. As it is, he's very much underpowered, but Riot doesn't have to be scared of nerfing him.
Kayle did need the nerf. More than just lichbane, she could Q and it alone would be incredibly painful. It's a very potent slow, so making it hurt too was just too much power in one skill.
Xerath didn't have skillshots. He had A skillshot with no followup unless his ult was on cooldown. That was lame for him and for everybody else. "Oh I got hit with Q? Oh well, there goes a chunk of my health, whatever. I can all in him now and there's nothing he can do" or "Oh he rooted himself. Time to hit him with a spear/rocket grab/hook/whateverskillshot for free" vs "Oh he cast R. I'm dead yay.". There are already multiple nuke from 100-0 champions in the game, almost all of which have more meaningful interaction than a line skillshot every few seconds that hurts.
Karma players were promised a late game with her rework. She got lategame nerfs in compensation for minor mid game buffs while losing all of her unique abilities. The reason I think it's okay for Karma players to be upset is because, unlike Skarner, the window of Riot even acknowledging her existence is long over, and she never got any sort of compensation for the net huge nerfs.
Urgot just got nerf after nerf after nerf after nerf, long after the meta had moved on from when he was relevant and unlike old Skarner there's nothing for Riot to be scared of in buffing him as near as I can tell. He's just been nerfed into the ground and never gotten anything for it for far too long.