AP tank items need nerfing

the amount of games i suffer from heavy ap mages building ap items that have massive ap with insane amounts of health making a high burt mages that can 1v3+ and its very unfair seeing that mages have alot of cc and damage they can literaly turn a game around and the fact they can be tank its adds no counterplay i try to get mr but my missing damage gets me killed due to lack of sustain due to tankyness this is unfair and ap tank items need heavy nerfing

Any tips for better play?