Kassadin is broken

All he does is q you in early game and it only cost 70 mana once he get lvl 2 you cant do anything because of his e and lvl 3 your done because if your a melee he could just use his q e w and your gonna ask you self wheres my hp and once he get lvl 6 its over even if he doesnt hit you with his r and w he still deal tons of damage because all he has to do is hit his q and e. NERF HIM PLEASE