Yes, they did, and here's why:
Champion Name - IP cost, RP cost
Ashe - 450, 260
Sivir - 450, 260
Kalista - 6300, 975
That's why. Sivir is a bizarre accident. Look for her to get an upcoming rework that guts her a la Tristana if her usage in competitive play isn't scaled back. Meanwhile, Doublelift scared the shit out of the bean-counters when he took Ashe and crapped all over Team Dignitas, whose ADC was running Kalista. Not to mention that Ashe comes with the starter pack, and only the newest of the newbies don't have her, so they really aren't even making the $2 or so in RP per player that she costs. And skins-wise, Kalista is relatively new, so it's easier to create fresh skins for her than it is for Ashe, to get even more money.
IOW, Kalista is a cash cow; Ashe is not. Which is why they want to keep Kalista a top tier pick, and keep Ashe out of the top tier. My conspiracy theory is that they only reason Ashe got a rework (and probably the only really good one I've seen so far) was that HotS is using an Ashe-clone as its go-to training character (at the very least, her W is exactly the same as Ashe's), and they wanted Ashe to get some exposure to make HotS look bad ("Hey, nice ranger, HotS. Too bad we got there first."). I don't think they predicted that Ashe was going to go from trash tier to top tier overnight; I think they wanted her to be more of a second-tier pick. ("Hey! It's my Gold I promos! Corki, Kalista, Sivir, and Graves have all been banned! Lucian's been picked away! Hey, I know! I'll bust out my Ashe! We're running a poke-comp, and she can counter Lucian... maybe?") I think that's what they were really going for. Instead, they got a champion who was an absolute BEAST in the right hands, capable of assassinating squishies, mauling tanks, and completely dunking lanes. Seriously, I was in a lane with four enemy team members, and ended up getting a quadra just by going ham with Ashe before the nerfs.