Congratulations, you've established that killing fighters is in fact better than not killing fighters, but that doesn't change the fact that putting heavy blasters on auto fire while you are engaging things with a plasma cannon will frequently overload and kill you. The option of dying is not superior to the option of dying. You also picked the absolute worst case for BPD and best case for heavy blaster. On the opposite end of the spectrum, two BPD will wipe out a wing of wasps faster than a heavy blaster and at a fraction of the flux cost (obviously the opposite extreme). The wasps might not be threatening but if you're fighting something else that is threatening at the same time, you will be much better off with a bunch of extra flux to utilize. Also, skills make BPD way more effective against fighters while not really doing anything for heavy blaster.
Once again, not arguing that BPD is a better, or even good option against fighters, just saying it does provide some value there in addition to the value it provides against missiles which add up in my opinion. Like I said, I have locusts if I'm getting swarmed, and I attempt to build my fleet to help against fighters, so I find that heavy blasters are much more likely to cause problems than solve anything. I have also clearly stated that the burst PD is primarily for an extra layer of security against missiles if the flares are already used (they have a long cool down) and/or I am shield flickering, so that I don't need to worry about paying super close attention to my rear and can focus on other things. I believe they also help the AI avoid stupid mistakes that cost me supplies which is valuable to me.
It's fine if you don't feel like that is sufficient justification for mounting them, but there's no need to go on a crusade to prove they are useless when there is clearly some value in mounting them. It's all subjective evaluations of cost vs benefit.