We don't need to go into AI behavior at this point. Nobody has indicated that they have the slightest clue as to how weapon tables work.
The SFB tables are hardly perfect. Disruptors and Photons actually started with the same probabilities. Storing energy over 2 turns gave the Photon an advantage, so SFB propped up the Dizzies with DERFCTS and UIM modules. To make our own tables, you simply have to determine energy input to damage ratios for given ranges, and differentiate weapons by expressing that ratio with different probability statements. In SFB, the basic equation for heavy weapons was 1 energy to 2 damage at minimum range, progressively dropping to 1 to 1 and 2 to 1 as range increased. That is, for both Disruptors and Photon Torpedoes, if you fired at medium range, you would average 1 point of damage fro every point of energy you put in the weapon. There are simply different ways to state '1' in terms of probability. The photon is easy: 1/2 x 2 = 1. The disruptor is more complicated, but when you add the 6 possibilities together and divide by 6, it comes out to '1.'
From here, you can start making more exotic probability ratios by moving the power to damage ratios inward, like the Hydran Fusion Gun, or outward, like the ISC PPD. There was a lot of cheese incorporated in the PPD, so it's not really a balanced weapon. The probabilities of that weapon and the Hydran HB were too complicated for easy math, so I lost interest in figuring them out, way back when.
Phasers all use a modified version of the same table, and since phasers are the same across all races, they make little difference. Seeking weapons are the only weapon of art in the game. I think the drone control limit actually derived from the number of phasers the Big E was equipped with. I personally think the phaser II races were given a raw deal by making them pay the same amount of energy for a weapon with 2/3s the power and a <100% chance of killing an incoming drone, but that's another story.