Perhaps they need to stop nerfing stuff nobody asked to get nerfed. The flamethrower was fun to use, but it was also necessary because of the broken amount of charger spawns that made it a vital weapon in battling these.
It's not a competitive game, there should be no need to nerf stuff unless it's broken beyond comprehension. In this case the charger spawns were utterly broken in many difficulties and missions, but instead they chose to "fix" the weapon instead of the spawns.