A question about posion, fire damage aftereffects.

[Rhygadon]

Yes, this is why it's often good to drop fire/poison on a big, slow-moving stack while you focus your other attacks on archers or fast attackers. The longer you wait to whittle down the burning stack, the more work the fire will do for you.

(Of course the -DEF effect pulls a bit in the other direction, but you can get the best of both worlds by attacking during the final round of the fire ...)