Getting outplayed by Anivia ER sure feels nice

It's fairly obvious that her q hits twice (or maybe just to me, cause every time riot says "hidden power" it's pretty overt to me) and nerfing her q more would make it possibly the worst skillshot in the game. Power should come out of her e and shoved into her other basic skills.

The problem with Anivia is not that she can do burst damage. It's the fact that there are no counterplay options dealing with her burst combo unless you stay away from her range and/or build tank.

Ziggs, another burst mage that is good at stalling, at least has a lot of counterplay attached to his kit. He has moderate aa range and his passive isn't his main damage source so he can't insta-burst by using passive alone. His Q is a projectile that you can see from miles away. His W is more of a utility option more than a burst option. His E also has travel delay. His R, albeit having a large radius, is also a delayed projectile that you can see from miles away and act accordingly. Anivia's counterplay can be summed up in one sentence: stay away from her or you get fucked. Does this sound like counterplay to you?

Zed's burst combos are also fast, but at least they are skillshots unlike Anivia. There are still ways to sidestep all of his combos. Yes he can gapclose and can put down squishy targets fairly easily, but there are counterplay options to his combos (sidestepping, buying Zhonyas, etc...), unlike an undodgeable combo like Anivia's ER. Many mages and assassins (such as Aurelion Sol for melee carries, divers and bruisers; Veigar with his R that is pretty much broken) suffer the same issue to some extent but their issues are not nearly as destructive as Anivia.

Mobile assassins aren't what breaks the game (barring tank Ekko, or Ekko in general). Abilities with no counterplay are.

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Okay, let me put it differently. If you had to simplify champion's power, you could divide it into 4 categories: Offensive power, Defensive power, Utility and Mobility. Now, if you give every champion the same amount of points (say 20), each champion would have different distribution.

Zed would be like 10/3/1/6 It's very good point distribution for an Assassin, and he does his role well. He doesn't need utility to preform well, and his mobility gives him enough safety to partially negate lack of defences.

Garen is 6/9/1/3 Perfect juggernaut, but he's just a brick. Once he gets behind he sucks because he has little utility (or mobility) he can rely on.

Urgot 6/8/5/1 Badly designed ADC. As ADC he's supposed to dish out damage, not carry with tankiness or utility. He has his niche use but he's always either too weak or too opressive

Now, if you look at certain champions that have been or are popular, you see certain pattern. Their point distrubution is close to 5/5/5/5, so they are often subject to changes/competitive spotlights/QQ. These are Gragas, Ekko, Yasuo, Orianna, Kalista. Champions focused into one of these (Vel'koz with like 15/1/3/1) or two (Braum 3/8/6/3) are considered as much more balanced.

Now take Anivia. She has no mobility and limited defense (3-4 i'd say, and only because of her passive). That means rest of her points are in utility or damage. Does this mean she should be allowed to dish out tons of damage and have enough utility to back it up? Yes it does. Does it fit mage gameplay? Yep. So i don't see problem here. If they were about to nerf her offensive power, she would need pretty big buffs elsewhere. Also remember, her kit is basically unchanged (except for small R change in MYMU) since her release.

Btw.: Do you know what broke the game? Hint: It's not unkillable tanks or damage creep. No. Back in S1-2 there were much sturdier tanks and ADCs/Mages had much more damage. It's Tanks (who are supposed to be defensive/utility oriented) with more damage, assasins (offensive/mobility) with more utility, and finally ADCs (straight up offensive) getting great defensive options. It's funny actually, balanced champion could never be balanced.

Then there are some champions that Riot doesn't give the full 20 points to and have other champions do what they do but better in every way. Champions who are in dire need of buffs or changes, 1 sided champions who people QQ because "100 - 0 with no items" and get nerfed yet they have virtually no other tools or tanks that do nothing else but absorb damage and barely better than others who have a host of other tools. 1 mobility tool for a melee should count the same in the power budget as range auto attacks, how else is the melee supposed to get to you otherwise.

Anivia has too high a power budget and is more like at 22 out of 20. She has close to the burst of an assassin yet has range and huge CC and a GA passive as well as massive range wave clear for sieges. Her weak point, her early, is negated by the fact she is range, has egg and once level 6 can just R to stall out the game until she hits her late game.

not all spell shields block all spells (black shield however does block the most, and sivir's the least, however sivir's can block multiple spells for the duration of it being 'proc'd' (an unlimited number of spells striking her within the same moment (such as an all in burst dive), except the ones, that it doesn't block of course) and spell effects. Banshee's veil has unique coding and WILL NOT block aoe from continuous spells (go check the league wikia page which discloses all the things about it if you want to increase your knowledge of champion ability interaction, though be warned it isn't fully updated for reworked champions and some old champions that had their abilities tweaked (nor does it rarely have info about tweaks to champions ON DIFFERENT MAPS though ocassionally it will be mentioned in the modification history section.

It is sad most items, abilities, tooltips, and in game information lacks any kind of clarity about this kind of thing but if you play with an item or champion A LOT (a few 10,000s of mastery points) you will start to see subtle things (many skins have unique in game effects such as small movement speed(5) boosts on preforming certain actions, random massive bonus damage to minions, reduced damage from certain champions or abilities, etc. Meant as fun Easter eggs and small 'lucky' performance boosts, and thematically (more important) make sense, having been in many fights where 1 damage makes all the difference in the world and occasionally also being SUPER EXECUTED by some unknown damage source for massive amounts when brought to extremely low health, but walking away and then suddenly execute damaged(9300 from 'unknown' in the damage read out) by a skin passive that only functions on X map when vs X champion (a certain freljord skin vs a certain anti-champion on ARAM as vague example).

EDIT: Just for some clarity, when I first started playing league some 6 or 7 years ago, one of the first things I did after hitting level 12 or so was read nearly every page on the league wiki, and eventually over time every champion entry and in-depth ability details (background mechanics interactions), though never a substitute for actually playing the champion and learning it, it helped me figure out things like: Ability interaction with items that SHOULD work with the champion but don't (lack of clarity things), sometimes this is intended sometimes its bugged, sometimes its a problem they can't fix but know about so disable functionality against certain ability interactions when they would interact as they might cause game breaking crashes or exploits (why sivir's spell shield does not block all spells or champion abilities, but can block multiple at once, etc), or scarily seemingly broken exploits that are actually intended interactions (Fizz E letting him make champion ults and long cooldowns "miss" but go on cooldown (malz ult, veigar R, etc. though occasionally these will reset. Other interesting things like ult resetting after going off and casting ,but because the client sees you "died" before casting it server side it is immediately refreshed(applies too with ziliean ult and guardians resurrect) (applies to point and click ults and certain abilities)). Over time I also researched every thread I could about a confusion champion or an ability or champion with weird item interaction (KAYLE & old Quinn make my brains ache), though rarely would there be any comments or information or clarity offered anywhere about a weird item idea or interaction (or ability interactions) making it difficult to tell if bug, fluke circumstance causing a weird thing to happen, etc. But over that same time it resulted in me committing rigorous testing of champions (that I own or can free play) to figure out these interactions, some things like the skin and odd map interaction differences I keep to myself or the research circle (friends) as I don't want to 'get cool special in game things busted.' But it's enjoyable to talk about them vaguely and encourage other people to seriously research things on their own (and play with what they love till they master it!)