Veigar ult one shot

So i know its been almost a year since Veigars ult got change to its current state where it is a execute ult, but veigars ult is still literally 100 to 0 people with no abilites but ult, R. An easy possible solution could be make the AP scaling dmg from ult to increase as the enemy gets lower, that way veigars have to land atleast an Q or W before clicking R for skill, because currently as veigar about 20-25 mins in on a average game you can just walk up to ADC and click R and they will die, which kinda goes against everything riot tried to change veigars to, they wanted to make it so veigar has to land atleast one other ability before wrecking them with ult, but that clearly isnt the case. Im not asking for veigars ult dmg to get completely nerfed, just saying for it to go along with the execute part of his ult, veigars ult shouldnt one shot people from full health. Simple solution make his ult do less dmg if the enemy if full or above 75% health