Flamethrower should have some sort of DoT effect, or even a Vulnerability effect. It should also ALLOW YOU TO TURN, like god damn.

Thinking more on it, Overheat needs either a drastic increase in damage, or a way to extend its duration, or a way to reduce the 'cool down' period.
Case A) A damage spike, a skill speed spike, removing combo requirements on the shots, or something along these lines
Case B) 'Cooldown' effectively extends the duration of 'Overheat', staving off the eventual shut down.
Case C) 'Cooldown' usage reduces the penalty timer, allowing you to get back into Gauss Barrel territory .