Yes, Kayle needed a nerf. **To her late-game.**
Kayle's early game is such unabated dog shit that she loses the vast majority of her lanes uncontested. It's that her late-game is such complete bullshit that every game with her tends to turn into a ticking time bomb - the same issue that Yi pretty much had for a while when he was rolling Feral Flare or Devourer. Every Kayle game I've ever been a part of turns into this:
* Kayle's lane is massacred.
* Kayle disappears from all team interaction for about 15 minutes while she takes pretty much all the farm everywhere.
* Kayle reappears at level 16 and massacres the entire enemy team while her team acts as a meat shield.
The only catch is for her to reach level 16, that's it. It's not contingent on her being horribly fed and full build - it's contingent on her gaining enough EXP and maybe having three items by the end of power-farming in order to wreck shit.
These nerfs don't fix Kayle - they make her worse to play with and as. Against? Sure, now it's a joy - instead of it being just relatively easy to stomp her in lane, it's now pretty much a guarantee. But that means anyone who picks Kayle now consigns their team to having to deal with a guaranteed losing lane (bar the jungler planting their fat ass top from now until oblivion, or the jungler being Kayle and them just effectively not having a jungler) as well as to them having a miserable first half of the game.
This is the same shit you did with Zed - you plugged so much power into his early-game that should he ever hit late-game he's a complete waste of space. Kayle's just the opposite with her being a complete waste of space early and relying on hitting an arbitrary level. What is with this "all or nothing" design on champions lately? It's either all one point or none of the points - there's no inbetween here, and it makes for horridly toxic design and gameplay.