If you have continuous beams do hard flux damage while keeping their range, they become hard counters to a lot of things. The issue is mainly qualitative, so tuning things like DPS or flux costs wouldn't be very effective. I.E. you'd have to tune their stats to be bad enough that a ship using them would run into peak performance problems; otherwise all it's doing is just making the kills slower but no less inevitable. To keep some kind of balance, you'd have to reduce beam range, which in turn would make them very similar to other energy weapons.
...which is why, when I made that work in Vacuum, Beams had the lowest range band or had a very long recharge time; that kept them nice and balanced in their niche; good in their prime roles (PD / anti-fighter) good for close assaults and DPS trading... but bad for kiting, where they're a real problem.
As it stands, Beams are potentially the most OP things in the game atm; a swarm of Beam-carrying ships can concentrate enough firepower to kill anything whilst kiting everything but the highest-range Large-slot weapons, which is bad. I've watched that happen with packs of Hegemony Wolves that spawned near Pirate Eagles; they crushed it easily. I haven't built a Wolf pack designed for that task myself this build, as I've been trying out everything else, but it's obvious that once the threshold has been reached, Beams are optimal killing devices. Pretty sure Wolf packs with 3 Tac Lasers, 1 PD in the center turret and all else built around range and survival are pretty powerful though.
The only thing that prevents this from being a major problem is largely the lack of enough High Tech ships with configurations that aren't terrible. If High Tech's Cruiser wasn't basically junk, if the Medusa wasn't more optimized as an alpha-strike machine, etc., this discussion would be quite different in nature, because the obvious issues with Beams having superior range to practically everything that matters would be more apparent. I'm still not entirely happy with this uncomfortable set of squirrel-cases; it means that High Tech will always need to be weirdly crippled to stay sane, rather than having flexible options.
I totally agree with Megas on LRPD / Burst PD / Heavy Burst PD, in terms of their current balance; there literally aren't good reasons to use any of them atm.
LRPD simply needs to rotate quickly enough to engage nearly instantly and have slightly higher DPS, so that its inefficiency isn't quite so crippling and its cost is justified.
Burst PD should get a buff to DPS or quite a few more charges or a faster charge rate when it hasn't been firing for X period, so that it's more like what it says on the tin.
Heavy Burst PD should get a 200 SU range buff and a bit more DPS, so that it has a distinct role from the lighter version, because it can hit things further out and be a better PD system in general. Right now it's largely a waste of OPs and because of the dearth of ships that can even mount it, it's not terribly relevant.
That leaves out the Beam nobody really uses, the Guardian, which is one of the most awesome-looking disappointments in the game, because it's sub-optimal for any of its purposes. I'd just drop the charges mechanic from it; then it would be useful in its role... if any High Tech ship was willing to give up a Large slot to a weak-DPS turret that doesn't do Hard Flux or if any Midline ships had Hybrid Large slots.
As things stand, I can't imagine a real role for it that is sensible in a serious game; the one-ship-fleet Paragon model pretty much requires the Large slots be used for DPS, and the Odyssey (which I have yet to encounter / buy in my current game) doesn't have good enough turret locations to make it work. Neither the Apogee nor the Aurora can mount one, so it's a weapon that literally doesn't have a sensible use case atm.
The best way to see it get used would be to fix up the Odyssey's turrets so that they're sensible, with the middle turret having a 360 and the others having appropriate dead spots to reflect that it's "higher", since that's the general idea behind the turret designs; that alone would probably make the Odyssey more viable in general and at least present one case where the Guardian might have an actual use, since that's a ship designed for broadside combat.