Enemy flamethrower = Bring chemspray 
used to be that way...but with gunners.
flamethrowers: bring heatsink.  and now that Heatsink and incendiary are about the same distance...well at least on the Lumberjack...the question a gunner asks is "do I want my gun, or do I want power?"
Goes with the typhon flak as well.
Though I haven't been able to play since the patch, from what I'm hearing...it's almost back to normal with flames...