Update: Kalista's PBE nerf originally put the champion at a 500 attack range at the time of this article's writing, a value that was later reverted to 525 which would put Kalista within the second-lowest tier.
A Kalista nerf that's currently being tested on the League of Legends PBE servers would reduce the marksman's auto attack range to the second-lowest value for any ADC.
The nerf in question (via Surrender@20) bumps Kalista's attack range down from 550 to 500, a reduction that doesn't seem like that a huge decrease but will actually have a fairly significant effect on those who are already used to the marksman's current range. Common ADCs like Tristana, Twitch, and Vayne all currently sit within the 550-range tier, and with those three champions as well as Kalista already pretty popular among various ranks, the nerf might be enough to make players gravitate towards other options instead.
Though the nerf will hurt Kalista and will affect trading patterns both in and outside of the laning phase, it at least doesn't put her completely underneath other ADCs in terms of range. Should the change go through, she will be among the second-lowest range of traditional ADCs though, a tier that includes other champions like Kog'Maw, Lucian, and Sivir. It's worth noting that other Graves sits at an even lower tier than the rest of the ADCs, but with the champion not usually played as a marksmen, Kalista and the otherst still sit at the lowest of the traditional ADC tier.