As far as I am concerned Mortar Halftrack is hardcounter to emplacements of all types, and should stay as such. This can only be the same as complaining Riflemen can't beat Tiger, so Tiger should get nerfed.
Ostheer players pays a lot to get a hardcounter that's very vulnerable to literally every other asset a British player has on hand, besides emplacements. ANd like others have said, such an option only occurs if s/he picked the right commander and saved the fuel and manpower for it, AND works hard to preserve the halftrack from easy destruction- they lose the halftrack, they are done, and at 30 fuel less, too.
Also, last I played, emplacements were decrewed with damaged, so it is possible to salvage the situation.
About the realism, if you have a hole in the ground, covered by sandbags, with 2 steel mortars and few people, what's gonna burn like crazy? Sand? Steel? Ground?
If I had to guess, it's probably the magnesium, phosphorous or thermite that is the payload of the incendiary weapon in question.
While we are on the topic of Flames, they really ought to revert the Flames sticking around for 20 seconds. I was using a Wasp while defending my Forward Supply Station and it got caught in the DOT. I was helpless as I watched my building burn down from my own Wasp's three second burst...
Serves you right for being so haphazard with the Queen's flamethrower...and destroying Crown property while you're at it, too!