Do not underestimate fire, as it ignores all normal armor, no matter how thick, and causes massive Morale loss.
A target hit by fire takes 5-10 damage, modified by its Fire Resistance. 2x2 targets take quadruple damage. An additional fire hit is dealt every turn the target is burning (which can last up to 5 turns).
Fire damage never deals Fatal Wounds.
Some enemies might be immune to fire, but those who aren't, will eventually succumb to it - especially since Flamers cause multiple hits.