Anivia has been in a weird spot for years now, her high mana costs and vulnerability as well as her quite boring kit made her an extremely uncommon pick.. which seemed to make her ability to one-shot people with Frostbite go under Riots radar.
It’s obvious to see Riots aims with these changes, make Anivia deal the same amount of damage but in a less gimmicky, more “skillful” way. Originally people would cast Frostbite (E) on somebody, and then place their Glacial Storm (R) beneath them before it hits, causing her Frostbite to deal maximum damage to them and quite often one-shot squishy targets.
So to prevent this Riot has made her ultimate “fully form”, where it slowly grows in size and damage and only once it has reached it’s full form will her Frostbite deal the 200% damage that it usually does. To accompany these nerfs though Riot has also made her Crystallize a much shorter cooldown at all ranks (25 seconds – 17 seconds at all ranks) which will make it much easier for Anivia’s to throw out what will become their main combo of R-W-E or W-R-Q-E..
My thoughts on these changes are that they are long overdue, although Anivia hasn’t been much of an issue in ranked games, pulling in a very low play rate.. that still doesn’t mean she shouldn’t be touched. Without giving her kit an overhaul comparable to Poppy’s, at least by making it require more skill to deal the same amount of damage will make her more balanced. However with her low play rate I doubt we’ll see the effects of these changes anytime soon.