Imho, the true problem here is with resistances. Fire (and other elements) deal far more damage than they should, because the player can find some lucky drop which cuts that damage entirely in half. So the numbers on fire damage have to be much higher to overcome this, and then you have characters who don't have fire resistance yet and get immediately roasted.
This could be solved by making both elemental damage and elemental resistances smaller; ie a fire dragon's breath deals about 35% less damage, but each rank of fire resistance only lowers damage by 10% (so you take 70% at rF+++). Numbers are ballparks, go ahead and tweak away
Imagine a hypothetical door which when you opened, the fire dragon and giant were both magically in melee range (no step required) and then they both hit you with melee. Do you think their melee damage could have one shot you?