I've wondered why I regularly fail 95th missions with my level 90 non-seasonal melee assassin when an enemy attacks me with a flamethrower or I'm on fire after killing him and so don't need to continue at all in the final missions of a Void Crusade. Now I know. The enemy fire damage is way too high and kills me instantly. That alone takes away any motivation to keep playing what is actually a damn good game because even at level 100, enemy fire damage will probably kill me instantly, no matter how good my gear, how appropriate my perks and passives, and everything else is. Until this is properly balanced and you have a chance to succeed in end-game leveling, it doesn't make sense to keep playing.  Even building a ranged fighter makes no sense anymore, because he fights mainly on single damage since he also constantly gets into melee combat and has no chance of survival, let alone success in that fire damage like it is now. Please devs fix it as soon as possible. 

You are absolutely right about this. There is no such defect in other types of damage. As you stated, even though I have 80% damage reduction and nearly 50% heat resistance, whatever the source of the fire damage is, it causes me to die instantly. In this regard, the producers definitely need to review the situation.

Ah. I see. Hidden DoTs. This is fatal, of course. Then I'll wait until you figure out why there's more DoT damage in there than just the fire damage itself, which with good fire resistance isn't nearly as devastating as it is now, and you've had time to bring this "damage feature" back to normal.