That isn't how it works. If you're firing above your own flux you're losing the flux war against someone who isn't unless the shield damage efficiency of the weapon is better than the inverse of their shield efficiency. The inefficiency of the heavy blaster is made up by the fact that its minimum damage versus armor number occurs at 2883 armor. Which means that at 500 armor its 37.5% efficient while the pulse laser against 500 armor is 15.1% efficient. That against a 500 armor target a heavy blaster takes 2 shots to strip it(for a total duration of 1 to 2 seconds) and consumes 1440 flux in the process(and does hull damage on top) while a pulse laser takes 19 shots to strip for a total duration of 6 to 6.3 seconds and consumes 2090 flux. And because a hammerhead has 500 armor.
On paper, it looks bad, but it practice, sometimes heavy blaster is more effective than pulse laser at winning the flux war (against inferior or equal opponents), then finishing off the enemy after the war is won, because of the higher DPS (and better anti-armor). I tried both, and often, Heavy Blaster is more effective overall, especially if the ship can only squeeze so much on its mounts. Also, what intrinsic_parity said.
Ultimately they are also shooting you, so the equation is really (e. dps * f. shield eff. + f. (wpn flux - diss)) < (f. dps * e. shield eff. + e. (wpn. flux - diss)) where e and f are enemy and friendly. If that equation is satisfied, you're winning the flux war. High dps definitely helps in that case as long as you're not increasing your own weapon flux too much.
This is a large reason why Heavy Blaster can be better than the more efficient Pulse Laser or (for some ships) the most efficient IR Pulse Laser. Energy weapon ranges are terrible! The ships using them WILL get shot back, and WILL take hard flux on shields from the enemy. Higher DPS can mitigate this because the enemy has less time to fire back before losing the flux war.
Not all enemies are single behemoths that take more than your flux bar to beat. Sometimes, it is a group, and taking out one isolated enemy quickly with superior DPS is nice.
Phase Lance with more range would be hideously overpowered... Due to the massive burst and being effectively histcan. This would be especially harmful to frigates, and don't most of them become effectively obsolete during a game run fast enough already? This is also in reply to later Phase Lance comments though I don't think I should go and quote a whole bunch of posts heh.
Even with Advanced Optics, Phase Lance is decently useful at best and a bit underwhelming at worst. Usually, I need hard flux support from other weapons to make it good. If anything, I feel like I pay too much OP for 800 range Phase Lance. 600 is so short than I usually take Pulse Laser over Phase Lance because the former does hard flux and the latter does not. Rarely is the burst more useful than hard flux.
For IR Pulse Laser, you mentioned same overall DPS, but you were not clear if you meant over a short period of time or sustained. Same overall DPS over say... three seconds would mean lower sustained DPS due to the initial burst spiking DPS over the first second or so.
As for spiking flux for IPDAI like TaLaR points out, I do not know what to make of that without trying it out. If it increases effective accuracy of PD because of "more dakka", then it may offset the flux spike. Likely users of IPDAI IRPL are large ships (Aurora, capitals), who are more able to take the flux spike.
As for double tac laser overpowered? Are you kidding me?! Even the test results shown by your videos seem a bit on the slow side, but acceptable for the job they do, which is a long-range finisher after shields are defeated. Tactical laser spam is not overpowered against the enemy (beams are slow at killing PD threats like those fighters and frigates, or stripping armor of big ships), and I seriously doubt one that is roughly double (somewhat less DPS, but better anti-armor) is too, if on a medium mount. If it was, I would not be clamoring for a long-range simple damage medium beam effective against non-shield defenses. (Could be new weapon, or could be phase lance or burst heavy laser getting at least 800 range.) I guess a double beam would be overpowered if it was in a small mount, but this is a valuable medium mount. Tactical laser in medium mount is underpowered, but it is the best option for long-range non-shield damage.