Between her shield and Deaths Dance, Kai'sa is not nearly as vulnerable to burst as she should be.
And that's a problem given how insane her damage is. It would be one thing if she were easy to burst down, but between the 30% damage mitigation on DD, all the healing on DD, and the big shield on her ult, Kai'sa is able to absorb far more burst than a typical adc while being able to outduel basically anyone. When a Kai'sa can beat bruisers and Juggernauts at melee range with equal gold, that's probably a sign that she's too tanky. This shouldn't be surprising either, given that we saw the exact same thing a couple years ago with Graves when he was building Death's Dance. 30% damage reduction is just too much on a ranged champion whose weakness is supposed to be burst. I honestly don't even think that Kai'sa herself is OP, but that DD gives her a level of survivability that makes her level of damage and pick potential overbearing. You can tell that Riot didn't see this coming either because despite the fact that almost every Kai'sa builds DD now, it's not one of her recommended items. She clearly wasn't intended to be this durable, but that's where we are now.
shield + 