Personally, I'm not all that familiar with the Master build, but here's my opinion on what Flamers and burn damage in general should be like:
1. Flamers are supposed to be incredibly powerful for their price, especially thanks to the burn damage that they inflict. However, this is balanced out by (or is supposed to balance out) the fact that they're the shortest-ranged weapons in the game. (If you think of the Machinegunner Cyborgs as being like Terran Marines from Starcraft, then Cyborg Flamers would be more like Protoss Zealots, which are themselves powerful, but short-ranged melee units.) Sadly, I feel as if alot of people on here fail to realize that the best way to deal with melee/short-ranged weapons is to simply stay away from them while you attack them with longer-ranged weapons.
2. Burn Damage should be multiplied by the weapon type of the "host weapon" affecting the target's unit or structure type. For example, the burn damage from a Flamer attacking a Hardpoint should be multiplied by only 10%, while the burn damage from a Flamer attacking a Bunker should be multiplied by a whopping 300%.
3. As far as how thermal armor should apply to burn damage, I have a couple suggestions:
- a. Ignore thermal armor altogether.
b. Apply thermal armor reductions to the total burn damage output, then divide it throughout the time that the burn damage lasts. For example, say that a unit with 10 thermal armor catches on fire, and (after applying weapon multipliers) would take 30 damage over 5 seconds, without applying thermal armor. When thermal armor is applied, then the afflicted unit would take 20 damage (30 fire damage total - 10 thermal armor) over 5 seconds, or 4 damage per second. Now if the target had, say, 35 thermal armor, then the damage taken would be 10 damage (1/3 x 30 fire damage due to high thermal armor) over 5 seconds, or only 2 damage per second.
Finally, I'd like to ask as to why the only structures that we can build that have Flamers, Infernoes, or Plasmite Flamers on them are all Bunkers? Pretty much every other weapon type in existence outranges Flamers, though that can be compensated by cleverly placing them behind hills (such as just behind that crater to the north of the LZ in Beta Mission 6). However, what really cripples them in my eyes is the fact that Flamer Bunkers are themselves weak to their own weapon, even more so than Cyborgs! As such, I wish that they were mounted on Emplacements instead of Bunkers (or Hardpoints or Towers). While still being low to the ground like Bunkers, Emplacements are treated as Hard Structures, meaning that Flamers are very ineffective against them.