OK, i had some time and did the math.
Every 5.33 points of rating versatility gives 1% dmg.
Every point of intellect rating gives 1 dmg total.
So lets see:
At 200 int: 5.33 vers gives 2 dmg total ( remember 1%), 2 int also give 2 dmg total -> ratio vers/int = 2.66/1
At 265 int: thats the point when vers/int ratio is at 2/1
BUT dont forget that your int still gets buffed by your vers rating. If you go full glasscannon you probably will also be at 10% vers. That means every point oft int will give 1.1 dmg total.
End of story, around an Intellect rating of 290-295 depending of your vers rating you can say, that 2 vers will give you an equal amount of total dmg as 1 intellect.
And at that point you will be Onebuttondmgvomitman9000