Anivia has never been about sieging or heavily CC'ing. She's been about stalling the game and become a late game monster with huge burst and great wave clear and zoning potential. Riot should change the ultimate to be a 1.5 second expansion in exchange for the maximum size no longer dealing increased damage, just increased chill duration and slow. Additionally, they should revert the Frostbite in order to punish bad Anivias and remove the slow increase on Flash Frost. If they truly wish to redefine the champion, they should increase the missile width of her Flash Frost in exchange for having her stun be a flat 1 second.
So let's talk about some things that changed:
Auto Attack Speed up. Yay! Genuinely, I felt like it could use a buff.
Anivia's Q deals 20 less damage and .1 less AP ratio. In exchange, it now has 1.5 seconds of stun and can slow for up to 40%
First, the increased "utility" concerning the slow is very close to irrelevant. The slow is for 3 seconds, and let's be honest during that time you're stunned for 1.5 seconds, and you're mostly going to be firing back your own spells against a no mobility Anivia rather than trying to move away.
Then, Anivia gets a .5 second longer stun (which makes no sense; she doesn't want to stay in for a long time even with the fact that her ultimate can come online a little tiny bit better. She's extremely squishy and with no mobility the last thing she wants to do is stick around, and a one second stun accomplished that job just as well)
In exchange, she lost .2 AP and 40 base damage (Q gets two procs of damage if used properly). On average, I can get 600 AP with a defensive build, which means 160 damage gets lost. That's a lot of damage for a not very useful .5 second stun increase.
Anivia's E now has a range increase of ~35 and moves 400 units faster.
One of the things to do with Anivia was E-R because of the slow missile speed with her E, which really separated good Anivias from bad ones. Additionally, bad Anivias might ultimate into E only to have that person walk out before the chilling effect can be used because of E's slow missile speed. By increasing her cast range and missile speed, this makes Anivia easier to play.
And then they have the stupidest mechanic, an expanding range size. I get you're REALLY excited that you can code expanding ranges, as evident by Aurelion Sol, but it is SO out of place for Anivia.
First off, the ultimate's very edge of the range in comparison is DOWN 190 units, a really huge deal. With those 190 units, I can slow into use my W/E in order to net a kill, which can no longer happen.
There's an increase on slow. This could be very, very useful, as Anivia is going to have an easier time hitting her Q... if they couldn't just walk out before it could expand to some sort of meaningfulness
Attack Speed slow is removed. Makes sense, as this made no real thematic changes for Anivia and was just kinda awkwardly placed there
Anivia no longer has her wave clear, which was one of the things that defined her: her stalling. Now, in order to achieve a similar effect, she must waste 255 mana in order to wave clear the minions, in addition to what she would have already been spending formerly.
And the elephant in the room, the expanding ultimate. This gets to be really, really, for lack of a better word retarded. She's losing damage on her Q so that her ultimate can get some extra damage and chill duration and slow, yes. But who in their right mind would stand in something for 3 seconds? At lower ELOs you can take advantage of the fact that some people don't know what it is, but it's really hard not to notice something that is getting bigger and dealing more and more damage.
What ends up happening is that anyone with even half a brain and any sort of mobility at all (Including something as small as Vayne's Q) would eat the chilled E and take maybe a tick of damage from her R and then walk out in order to wreck her now that she needs to land her Q. And how does landing Q-R work? You R first, they walk out of range of the ultimate and you miss another proc on E because it's impossible to hit Q. You try to just throw your Q and they walk out of range because of its extremely slow moving speed. What ends up happening is that you sit on your hands and wait for them to hop onto you, which creates very lackluster gameplay and ends up being a farm-fest.
I believe her overall gameplay changes in a dramatic way as a result of these changes, to the point where playing her like it had been formerly becomes virtually impossible. Her "already-potent CC" was never truly there, as Q was difficult to hit at best, and in most situations had only hit one person, maybe two. Increasing the size of her Q could lead into hitting multiple champions, and would truly make her have CC in the manner that she should be reworked to have.
Her E is a point of discontent for me. It's not that I particularly hate that change, it's just that as someone who has spent hundreds of hours playing this champion (and that is quite literal), this feels like nullifying a lot of the work I have done to be better than some of the other Anivias.
Her ultimate is clunky and out of place. This may be because I'm trying to relearn this champion, but I feel like this is compromising what it truly meant to play Anivia. One of the greatest things about Anivia was placing her ultimate in such a way that it caught a fleeing person and killed them while it slowed another for an E or a Q and killed him too. The 150 units that it starts at is just too tiny to have any play with, and she becomes very flat rather than a dynamic character. Her ultimate now becomes "Will they sit in it for 3 seconds?" and "Should I forgo getting another proc of E to make sure I get more damage on R" which stales gameplay. Being just barely able to move and wiggle so that my E can proc off another time, using her low mobility to dodge skillshots, they were things that I enjoyed about Anivia. They no longer apply.
Anyway, sorry about the long rant. I needed to say these things because as a long-time Anivia player I feel like she's been nerfed and has lost a lot of her character. Thanks for reading