Kalista has been a problem since she's so good if you are skilled with her, but she's terrible if you suck. So when she's weak, the average casual player sucks with her, but when she's strong, the excellent Kalista players dominate way too hard. I don't think a range nerf is a terrible idea--since she has so much inherent mobility, this can make up for her poor range and make her play a little more risky to do well--but 500 seems a little harsh 525 would at least put her on par with Xayah, Jinx, Karma, Quinn: low, but not unworkable with other abilities in mind.
Then again, looking at 500, when it comes to relevant lane opponents, you've got Kog'Maw, who has a range modifier and 0 escape, Lucian, who's pretty mobile and has to play a little risky in order to be fair, Kindred (I guess), who has a short CD dash (or flip, whatever it is), and Sivir, who probably has the hardest time but also has a spell shield and can shove the daylights out of a lane. So Kalista would not be out of place. We'll see where this puts her, I'm leaning towards too harsh a nerf, but after glancing at the range listings, it could go either way.
Kalista just spent months as pick/ban at high MMR and essentially permabanned professionally and they didn't do anything. Meanwhile, Vayne was strong for like 2 patches and they nerfed her. So I don't think the argument of "LC$" or whatever is valid here. When will people understand that Riot doesn't favor the same Champions all the time "because LCS"? Do you not realize that seeing the same few champs actually HURTS the viewing experience in general, no matter how fun they are to watch?
and 
but especially 
who was sitting at a 54% winrate didn't get nerfed even 1/2 as hard can you imagine how low her winrate would fall if Riot suddenly reduced her AA range to 500? This is a legitimate champion killing nerf, and it's only being done for the LC$.
problem, is broken in highest level of play so they change it.
also isn't she an adc with 90% AA damage modifier instead of 100%?
