Does a DoT's damage use the numbers like crit bonus and potency from the time it was cast or does it calculate those numbers for every tick? The reason I am asking is I currently use the potency charm from Lord Vyemm that does +100pot+2%/2sec for 40 seconds. I just recently won a Diabo Seal of Noxious Focus charm that gives +480potency to all Noxious and takes 200pot from all Arcane/Elemental. It lasts for 8seconds. If I had a DoT running for 30 seconds that kept that +480 the whole time it would be great, but if it only used it for 8 seconds of ticks then went to normal potency that wouldn't be so good.
I'm pretty sure everything is calculated when the spell is cast, like when a DOT is doublecast all the ticks are doublecast ... You could always try it in game and check the combat log or ACT parse to know for sure.
