Why are mages so strong?
A fed mage beats the fed equivalent of like any other class. Fighter, assassin, support, adc, bruiser. etc. The only class that can stand up to mages is situationally tanks and only certain types. Take annie for example.
A fed annie WILL one shot any role except for tanks and no other role can contest the impact of an annie. Same thing for brand, anivia and malz. You can argue a fed fighter/adc/assassin is strong but they don't have the burst, CC, or AOE damage that a fed mage provides. A fed fighter can nuke one champ at a time while a fed mage can literally win an entire team fight with one ability.
Mages cant 1v5 and kill like 3 people no matter how much dmg they do if the get cc'd they can be bursted

These champions at least can all survive an Annie Burst by using their innate durability or abilities in their kit. Also, MANY Fighters can nuke multiple champions with their abilities, such as: