I never got anything done with it. I think it’s completely useless. The cone doesn’t indicate any result and I feel like the outcome is completely random. The AI seems to handle it quite alright, though.
I’m not 100% certain but I think any sort of cover barrier blocks it and it won’t do very much to an armoured target. Similar to grenades just move the cone over the target until you get some white to show up in the long red bar. I haven’t used it enough to know where the best part is but if you get that white indication damage will be done and I think it stacks with a flat 40 burn damage for anyone caught in the cone, that is caused by the fire itself.
So it’s less useful late game but it’s kind of fun as a hit and run weapon from out the back of an armadillo in a Phoenix Point style drive by.