So much this!
This whole splash damage concept is a joke anyways. Shoot the ground but not the zed itself to deal more damage... c'mon.
The problem with the firebug is that it's the wheelchair under the perks with the lowest skill ceilling but is super overpowered. That's why it's the preferred perk of players that tend to cause problems...
I'm okay with the concept of having an easy to play perk for Joshiro, when he does his live streamings. But that shouldn't consist solely of area-of-effect weapons that allow to hose down one side of the map for a full wave. The firebug should be only temporarily able to provide area denial, due to limited ammo. There should be a gun like the MAC-10 for the rest of the time, that brings the firebug better in line with what most other perks do: Actually aiming.
I guess you have no idea how Napalm works, because that's exactly what's designed to do: It's a glob of flaming jelly that cannot be put out, as it burns real slow, yet at the same time, burns real hot. As of right now, the only reason I'm seeing Firebugs at all is because of the skills (Pyre and Splash Damage HUEHUEHUE) and how the Microwave gun works (which is totally derpy as hell).
However, Flamethrowers were designed to push people out of areas or threaten them with a gruesome, painful death, and the napalm helps in this ordeal, as it can stick to the area and burn for a long while, preventing others from moving into the area. Would the firewall do more damage than actually hitting the target? No, but it's there as a way to threaten zeds to either: find a different route and take it instead, or risk going through the fire wall and possibly dying. Seems like your entire post is about how derpy is the Microwave gun, and if so, I agree. The Microwave gun, out of any fire weapon, sounds like a weapon that should be concentrating it's fire on a target, never letting go of the trigger, or moving the heat off of the target.