Anivia feels bad now
I understand the intention of making glacial storm a smaller aoe that grows in time. It theoretically adds more power to extended conflicts. I however have several problems with this. It makes her even riskier and less reliable to play. It makes her have to get substantially closer then any anivia player should get to get burst damage from her e. On top of her having to get close she is so mana dependent that people have to build squishy items which is yet another reason for her to not get close. So how more people will start playing anivia is by playing her even more passively then she use to be played. I feel like that is the exact opposite response that this change was made for.
I honestly feel like the anivia changes were rushed. All of her core items got changed in some way and she was made less reliable by her ult being so tiny and taking so long to get big. So to sum up Anivia changes in my mind. Her ult became less reliable and risky to use making her play more passive/get bullied harder early. The increased slow and damage on ult are pretty mediocre because of how hard it is to get someone in the ult after 3 seconds. Her q having more cc is rather meh because Q is maxed last but on the same token losing some damage on her q makes her weaker at trading. Thus again promoting a farm fest. The faster E is nice and the faster aa is nice. The items that give Anivia good mana are not really tailored for her playstyle unless you build glass canon. Just my 2 cents. I think you should have waited to see how the items affected her before changing her.