How to maximize poison,fire

it’s about damage dealt over a few turns

It certainly is…

Maximizing damage over time seems much like any attacking special in that you want attack buffs and defense debuffs going off first. A key element in war or raids is making sure opponent has no dispeller or you have killed that hero.

Elemental buffs and debuffs like firing G Falcon before Gravemaker works real fine

Damage over Time increases with (a) hero attack stat and (b) troop attack modifier. Specials do NOT affect DoT, either plus or minus. E.g., you’ll get the same DoT when cast by a stunned hero against a defense-buffed foe, as you would casting from an attack-buffed hero against a defense-debuffed foe.

Keep in mind that Aeron’s special prevents ailments, including DoT, from attaching. Also a hero that is either blinded or under Wu’s buff have a chance to miss their DoT.