I disagree. Very rarely would i see a mage die to an assassin pre 6 in the past. Now if ur mage hasnt died to the assassin by lv 4 you are surprised.
It used to be that assassins DID get harrassed into oblivion for at least the first 4 levels. In fact the common answer to first pick assassins was to pick a good harass champ into them for the stronger lvs 1-5. It was common knowledge even that the assassin should be 20+ cs down by lv 6 if the mage was any good. Most mid laners would get judged by how well they did their job of harassing the assassin pre 6. They would also get heavily criticized if the assassin was allowed to roam pre 6. This was all because assassins relied on their ult to kill people.
If you died to a kat, kass, talon, dianna, or akali pre 6 a few years ago, you would be reported for inting or trolling cause you had to be seriously bad to have that happen. Dying to fizz and zed pre 6 was more likely but still not common either. Also even at lv 6, no assassin had 100-0 kill pressure even with ignite unless you where over extended.
If u dont remember that then you havent played for very long. I have mained mid since season 1. Both assassins and mages.
It all started to change with the addition of keystones.
That was when assassins gained more damage from masteries, better wave clear, more sustain, and more threat early. Riot kept increasing assassin base damage for no reason. Kassadin got increased damage and shield on q so he could trade early. Akali was given more sustain and an extra dash for free. Talon was reworked to have kill pressure lv 2. The assassin rework really changed assassins at all stages of the game.