Yes, I am aware that the damage is stacked on the whole, not every instance of damage, that is how I did my calculations. By refering to Thottbot's Mage page, you can see that a Rank 11 Arcane Missile deals 280 damage every second over 5 seconds adding up to a total of 1400 damage. So thank you for your response, but please be sure to fully read as I quite clearly stated the total damage not the damage every second.