Tiny things about Kai'sa that do disturb
Whoever paid attention a few days ago will know that I have a nearly biased liking for Kai'sa since i announced a thank you for her very creation, but having played her more and more, i've come to realize there are certain aspects about her that make her drop-dead annoying to deal with or, if it became famous, obnoxiously difficult to deal with.
-
Her Q ability procs the full animation even if she dies mid-cast. I have seen it a few times and made it work myself, but Kai'sas Q ability procs the full missile damage even though she might die while the cast still goes on. Firing one Missile then die should, if you ask me, prevent the other five from getting off. I have scored many 1v1 revenge-kills in the sense that if I died, so did my enemy, without fail and got fed that way until the enemy team begged/shamed/flamed me for it. An ADC should not be rewarded for being played like a Karthus.
-
She makes one of the most toxic and broken itemizations possible. A hybrid build of EVERYTHING.
Especially her synergy with and because unlike EVERY OTHER item-pair that shares the same core-item, those two have no shared cooldowns as active items. I rush this thing myself EVERY GAME, paired with a and Lethal Tempo mastery, to become so stupidly broken that not even a Malphite can fight, let alone counter me anymore. Gunblade and Bork should be hotfixed to share the same Active cooldowns since both share the same core-Item for the active, which is 
that way, not only would it be overall fair because then truly every item-pairs ingame would share cooldowns from their Core-items but it would also remove something that might make kai'sa very troublesome in the inevitable near future.
The playerbase already have tons of experience with problems Riot leaves unchecked until it becomes too late. Actually, it would not be surprising at all if Riot ended up even empathizing Kai'sa to be build hybrid and not as an ADC, and get her into the same coinflip-balance loop in which half the champion pool is already stuck.
? Sure, the durability might be nice, but it takes too long to stack for when she'd be able to get it. Plus, it puts her AP back into her autos again (One of the reasons it's core on Diana and Teemo - It gives them basic stats they want and amplifies their already existing AP on hit.).