I just got ks'd on a mob I had at 70% by a necro. I've been hearing dot damage instantly counts full damage the first time it ticks on a mob is that the case?
It goes by "ticks". 6 second intervals of the same amount of dmg (non focused) every 6 seconds. The real answer is you were hoping your dot ticks could out dmg the necro who applied vots then lifetap spammed. Douchenecro wins every time in that case.
You are correct. The full potential damage of a dot counts even if the mob dies before the dot completes.
It's a myth that it applies full damage right away. If it did you could Disease Cloud a mob with 40 HP and be guaranteed the kill. It doesn't actually work like this though and if you don't believe me feel free to spin up a couple of level 1 toons and test it on some decaying skellys From what i've seen there is no consistent rule for how dots calculate in DPS races. But it seems like MOST of the revamped dots give you 2 bonus Ticks. So if a Necro Ebolt a mob and it ticks once for 351 damage it will actually count for 1053.
It's completely messed up. I was KSed by a manchild shaman in Kod'Taz yesterday. He only did 24% of the damage to the mob but he got credit for the kill. He casted his three main DoTs twice each within twenty seconds because he knew what he was doing (then feigned ignorance, of course). Maybe bringing more attention to this will allow it to be abused more until DPG fixes it.
Dot damage from certain dots like envenomed bolt aka poison dots counts as full damage as soon as it ticks once. Test it yourself to see if you don't believe me.