So, I recently released an alpha version of a mod:
Corvidae Light Industries, and one of the included hulls uses LR PD Lasers.
Let's go through the problems:
One: They cost an absurd 100 flux per second. Well, okay, I'm designing this hull to have LRPD as built-in weapons; I can just increase the base vent rate. Let's ignore this problem.
Two: They can't stay on target. Even with Advanced Turret Gyros, they lose lock
constantly. Alright. Built-in hullmod that doubles the tracking rate of all beam weapons. Solved - at least as long as you're willing to
also install Advanced Turret Gyros. Moving on.
Three: Even when they
can stay on target, they don't reliably kill missiles. Sometimes they'll kill salamanders, that have nice long arcing flight paths that keep them under fire for quite a while. Sometimes they won't. Hrm. Well... the ship has a High Energy Focus system; if you're willing to use that to boost your PD, then your PD will actually work. I guess.
However, other hulls don't have the same advantages. I'd like to point out that the damage on LRPD (as well as the basic PDLaser, as well as all of the burst PD weapons, not to mention the humble mining laser) were originally set when you got bonus energy damage from high flux levels - and these numbers were never updated when that feature was removed.
I don't have any specific suggestions for fixes - any changes would require playtesting that I haven't done outside of the one case described above - but the LRPD in particular clearly needs help; as it is, it's simply not worth using if you have any choice in the matter.