What stage in the game are assassins meant to be weak? Especially as a mage.

I've been trying to get 's mastery chest for hrmm, about 7 months now and always seem run into assassins mid, and can't find any point in the game at which they are weaker than her.

Out cs's early and scales strongly late while Anivia falls off after 40 minutes. Can deal 40% damage with a single auto.

goes alright until he hits 6 then he clicks on me outside my spell range and kills me or at least threatens to do so, then proceeds to out cs me for the first 25 minutes and outscale me late

feels the most doable, but can push and roam to put pressure across the map or pick up kills; one-shots late game

Can shroud pre-6 to avoid any damage, outtrades, and has infinite sustain early, focing a back while I run out of mana after five spells, keeps infinite sustain late and can 1v5

Can dodge on reaction to avoid all damage then all in on anivia's cooldowns, forces trades and can tower dive with impunity. Late game can also 3-for-1

Literally infinite sustain with lower cooldowns than Anivia, knives to hop around freely avoiding damage, ult demolishes entire team late

Windwall invalidates damage from spells and dash invalidates both R and W; can out farm then combo into ult +2 autos to destroy egg form late

E pulls out of tower after her dive, her poke scales better, and her passive lets her stay in lane early

I haven't played against a Talon yet so maybe that's an assassin that actually falls off, but it seems like the class just scales far better than mages. I'm using Anivia as the example more than just because I'm trying to get her chest- she also is supposed to be a hallmark for a mage that scales into late game, but the Assassins mid seem to just get better and better the later the game goes.

Is the trick to just give up trying to get farm entirely and buy and just try to provide team support with crowd control and area denial?