Damage is slow at first, but can increase over time to a maximum of 578% weapon damage as Poison."
It takes 3 seconds for it to build to max damage. Half the damage is done immediately, the other half hits as as a dot divided over 3 seconds. After 3 seconds you do full damage until you stop channeling -- and your damage continues for 3 more seconds.
The dudes name was Nubtro, he calculated how the damage works. Link.
Good stuff - we could really use a summary, though. I read/re-read/re-read trying to understand it.
Honestly, I didn't get that half the damage is front loaded. Unless I misread it, the damage appears to work like this:
Each damage stack does 270% weapon damage.
You can get up to 5 damage stacks depending on how long you channel the skill.
How quickly you get 5 stacks is based on your attack speed.
From his examples, it appears that with:
1.0 aps you get 5 stacks in 2.2 seconds
1.5 aps you get 5 stacks in 1.4 seconds
2.0 aps you get 5 stacks in 1.2 seconds
How fast each stack does its damage is based on how high your attack speed is.
From his examples it appears that with
1.0 aps you get the 270% damage over 5.25 seconds
1.5 aps you get the 270% damage over 3.75 seconds
2.0 aps you get the 270% damage over 2.75 seconds
2.5 aps you get the 270% damage over 2.75 seconds
3.0 aps you get the 270% damage over 2 seconds