@Torchlight2 Plus: Indeed, Armor does not work for mitigating Burn Damage over time. My pure Focus Embermage used to die to it in spite of using the best available potions. When I investigated I found that he was taking much more damage than intended from Burn inflicted from the Fire Trap. Burn inflicted from enemy Monsters seems to behave correctly.

Nice find! Explains why some of my characters melted when touching the fire traps while others did have some resistance to it. Burning damage over time also ignores armor. %Fire/All damage reduce does help tough.