What bugs me about the whole Kalista thing
A while ago (Season 3? 4? I forget) Riot nerfed ALL the AS slows in the game. Nasus's Wither. Malphite's Ground slam. Frozen heart. Randuin's Omen. All of them nerfed to some degree in their ability to reduce AS.
Now we have Kalista. A champion whose kiting power is gated by AS, and for whom AS slows are one of her few weaknesses, thanks to her passive. Maybe we could deal with her when AS slows were stronger (aka you can slow her attacks long enough to catch and possibly kill her) but now it feels impossible to deal with her without multiple gap closers combined with high burst/strong CC. All of which is a huge problem for less mobile champions (read: most of the champions that are 'out of meta').
Basically what makes me frustrated by Kalista is that in order to deal with how powerful she is purely due to the combination of her passive, slow, and ult, you need to find solutions that are problematic in one way (boosting the power of AS slows causes problems for the ADC role on the whole) or another (finding champions who have the ability to take her out of the fight solo or as part of a team restricts team composition against her, signifying counterplay problems). As such she seems to be the kind of champion that breaks the game inherently towards remaining as it is now. Point-and-click champions can hit her regardless of how she moves around the battlefield. Extremely mobile champions can chase after her long enough to kill her (oh wait, sorry, extremely mobile champions with multiple gapclosers like her). So if you dont have either of these, the onus is on the Kalista to mess up, else there is not much you can do.
Inasmuch as Riot is directing this game towards a more tactics based game with 'twitch plays' as opposed to a strategic one, Kalista is a champion which requires strategic picks to counter because her high reflex intensive gameplay invalidates most skillshot reliant champions once she gets going. I fear that if they continue to remove targeted abilities, we will get to the point where her only weakness will be AS slows (and even then, those wouldnt affect her as much as, say, Vayne)