The way I see it, it's generally a tradeoff between heatsink and incendiary.
Heatsink is great on the light flak and is second only to burst in terms of dmg per clip. The reduction in clip and fire rate from incendiary are too much.
The difference between incendiary range and greased/heatsink on a hades is too little to make it work in my opinion. The dps is too low.
I experimented with double/triple incendiary carronades at one point, it's entertaining atleast.
I have found a use for incendiary on lumberfish and flak spires. The extra 40 meters (compared to heatsink/greased) for lumberjack has some use as an alternative to lochnagar. I like lesmok heatsink incendiary/greased/loch.
For the flak it's about 60 meters less than heatsink. In many cases I'd still prefer heatsink, but incendiary can work. I wouldn't bring a gunner on a flak spire though. My preference is spanner mallet buff charged/loch.
What I can see work though is when you pair an incendiary mortar not with a piercing gun, but with a carronade or even an artemis and disable the living hell outta them and when the armor does die you can use normal mortar for maximum dps and kill them in one clip. But then again, a banshee might do better...
I'm not a fan of incendiary mortar. I find that burst mortar is fairly effective against components, wears down armor/balloon, and starts some fires. I love carro + burst mortar pyra.
Does anyone know if there are two fire stack chances from double explosive weapons? A chance for primary and a chance when dealing AOE?