I have never used phosphorous ammunition in vanilla, and I don't suspect many others have bothered with them either. They do almost zero damage, even to unarmoured civilians. Testing in TFTD, I tried giving my dudes 500% vulnerability to phosphorous attacks, then launched a PH torpedo in a full Triton - this managed to kill about 30-40% of the crew in one hit. It seems like this is the bare minimum vulnerability unarmoured creatures should have to the stuff.
Going through the rule files, I see that whenever there's a difference between resistance to PH and resistance to regular fire, PH resistance is usually higher. There's the hallucinoid which has a particular vulnerability to PH at 70%, but that's still practically nothing. The PH torpedo is said to deal 80 damage, but this pertains to area of effect rather than damage dealt - none of my dudes in my above example had as much as 80 HP, and most survived even with 500% vulnerability (they all croaked on the subsequent turn, though).
And sure, incendiary deals damage over multiple turns, but so long as creatures are still able to function normally for all those turns, what is the point? And certainly, anything below 2.0 (200%) damage modifier is perfectly negligible. But what are people's thoughts on this? What would strike a good balance?
