Kai'sa only champ that can rush rageblade, because she's op.
Kayle? Nope, needs nashors and cooldowns. Kai'sa? Nope, has innate kayle effect and very powerful AUTO AIM burst skill on a 5 second cooldown. She doesn't need nashor's to kick in.
Now we have the most mobile ADC with Kayle damage and stealth. Alright makes complete sense.
We didn't mention that she can stop at two items and go purely defensive after that and still do top damage?