One thing Valve should do with the Backburner is to properly set the crit flag when behind an enemy to the same one when the Spy lands a backstab. I always have to face the small of my target's back to land crits with my Backburner. If Valve were to update this, the crits would be more consistent and possibly denerf the Backburner.
This. I can't believe how often I can't manage to get the Backburner to do the one thing it was designed for. If they fix this, they can take the regular damage levels back down to match the regular flamethrower for all I care.