I'd classify the flamer as medium range rather.
Not that history should dictate balance, but historically Pioneers and Engineers were elite units and had among the highest mortality rates. I think they should be a little bit more badass considering their actual roles.
Flamer has a range 20 and completely flat DPS so it better used at that range.
At that range pio smgs contribution to DPS (actually they are usually behind the flamer and thus further away) is minimal. C.E get DPS from their 3 mosins.