If anything, I think the flamethrower is UNDER-powered. It has a lot of splash damage, sure, but you have to hit someone either point-blank or with an extended burst to actually kill them. I threw a lot of fire out last night, but only got two kills. Got a few assists, but lots of guys managed to shoot me while on fire, and not die themselves.
If anything, they could reduce the ammo supply for it. You can use it a LOT without running out. But damage-wise, it's weak enough already.
Edit: It is effective as an attacker, once an M-com is armed, to prevent defenders from disarming it. Just keep that station bathed in fire. That was fun.