The fact that big energy gets such small + Dam Mods (PPC Caps out at +10, a 20% increase. LRMs get +2 per 4 Damage Missile, SRMS +4 per 8 Damage missile, a 50% Increase) serves to make bad worse. The very large stability damage bonuses on PPCs (+30 at the ++ level) close, but do not remove, the gap between the PPC and the LRM 20 - LRM 20 does 40 Stability, and another 40 with +2 Stability Damage mods. The PPC does 20, and gains 30 from the ++ level stability damage mod.
And as discussed, the LRM has a typical damage yield of 80 base, to which those larger boni are applied, so 120 damage on an 18 Total Ton weapon system, vs 60 Damage on a 20 Total Ton PPC (assuming fully sinked).
Really, LRMs/SRMs are the Proud Nails of game balance right now, and everything else is just whistling past graveyards until damage and bonus variants are brought in line with the other weapons.