Setting an enemy on Fire (via Fire shot, Death Fire or Flamethrower)
Each “hit” is 25% of your Loadout Attack, there is 1 hit per 0.25 seconds and there are 7 hits.
Improved Fire Shots doubles this to 50%.
This was buffed in 1.11, previously it was 15% and 30% respectively.
If you are using Flamethrower, while the enemy is in the flame there’s also 60% of Loadout Attack every 0.2 seconds. Note that this hasn’t been buffed in 1.11.
Poisoning an Enemy (via Poison shot, Death Poison or Dr. Toxic’s Venom)
Each poison “hit” is 60% of your Loadout Attack and there is 1 hit per second indefinitely.
Improved Poison shots doubles this to 120%.
This was buffed in 1.11, previously it was 30% and 60% respectively.
Dr. Toxic’s Venom shots hit at 30% of Loadout attack, as it was prior to 1.11.
Flamethrower is useful for actively burning an enemy (especially without getting hit - e.g. through ice in Ice event/castle) but not so useful for setting them on fire and moving away
I think DeathFire is rather useless - it does a bit of damage and then it’s gone (but the 7 x 25% = 175% damage is still more than the 75% that Death Blast delivers, although it takes the Death Fire 1.75 seconds to do the damage that the death blast does more or less instantly)
If you had to choose between Fire shots and Poison shots, I think poison is better if you’ve got a lot of spread shots + bouncy that are only occasionally hitting, but otherwise fire is better (you are likely reigniting them before the fire goes out)