Why is 1:1 flux a death sentence?
Other guns offer something else, like energy weapons giving armor crack, or EMP or such. Kinetic or HE weapons give you doubled eff in certain cases. A Pulse Laser is always going to either be a net neutral for you or worse. You're doing the same amount of damage to yourself as you are dishing out. Hence why every other energy weapon that has low hit str also has <1.0 efficiency.
While the Pulser Laser may need some improvements, I would argue there is nothing special about the 1.0 efficiency line itself, at least for hard flux weapons. Simply because weapons don't exist alone in space and have to be fitted to ships which have flux dissipation and shield efficiency values.
Firing a 0.8 efficient IR pulse laser into a shield with 0.6 efficiency (say a Medusa) is having "you doing more damage to yourself then you are dishing out". For each 1.0 hard flux you cause to the enemy ship, you've raised your own soft flux by 1.33. That's even true of something like a Heavy Autocannon (0.5 efficient against shields) firing into a Medusa's shields with Hardened Shields and a Field Modulation officer (0.43 efficiency shield).
The nature of soft flux being removable while shields are up and baseline ship dissipation of course renders that analysis inapplicable in game. So for the same reason that you put might put IR Pulse on a ship and still fire them at Medusa, you might put a 1.0 efficient energy weapon on as well.
I find the arguments comparing to the other low damage per hit energy weapons to be more persuasive. Or the fact that Wolves are over fluxed with the Pulse + Ion cannon combination, unless s-modded, in a fleet with Flux Reguation, and piloted by an officer with Ordinance Expertise or elite Energy Weapon Mastery (or both). Assuming something like 30 OP on weapons (Pulse Laser, Ion cannon, 2x Double Atropos, 2x PD Laser), a pair of s-mods, you can get flux neutral with shields up and firing the Pulse Laser and Ion cannon on a Wolf (150 base + 15 Flux Regulation + 150 vents + 30 s-mod flux distributor + 60 Ordinance Expertise - 30 s-mod stabilized shields = 375 vs 360). If you include the PD, then it's still slightly over even with elite Energy Weapon Mastery (375 vs 396). But that's basically throwing everything and the kitchen sink at it just to be not overly fluxed out.
On the other hand, 300 DPS is on the higher end of raw weapon DPS for medium ballistic/energy mounts (6 have more raw DPS, 12 less), and there typically is a cost to pay for that in some way. It just that DPS doesn't actually happen against armor on larger enemies (cruisers and up, and the occasional Enforcer), although against hull it is pretty respectable. Unlike say, Plasma Cannons, which are terrifying because they have amazing anti-armor performance that has decent shield performance. Dropping shields won't save you. A cruiser dropping shields against Pulse Lasers will save it.
Overall, I think dropping efficiency to 0.66 (i.e. the 200 flux/second) while maintaining 300 DPS would be too extreme, as that's pushing very close to kinetic efficiency territory while still having better than autocannon/needler anti-armor and reasonable anti-hull DPS.
I look at it this way, 2 Pulse Lasers is 600 DPS for 600 flux/second right now (1.0 efficiency).
A Heavy Autocannon and a Heavy Mortar is 538 shield DPS, 547 armor DPS (although really depends on how much armor), and 434 Hull DPS (again depends on residual armor) for 394 flux/second (0.73, 0.72, 0.9).
Dropping to 200 flux/second is 0.66 flux/damage to shields, better than the mixed ballistics case. Even comparing to a Heavy Needler + Heavy Mortar is 380/610 = 0.62, which isn't that far off, with nearly identical shield through put, and better armor/hull through put.
I could see 240 flux/second (0.8 efficiency), as that matches IR Pulse and Autopulse, and doesn't come across as just being plain better than the mixed ballistics case. It's also the ratio I'd expect to balance against a kinetic + HE mixture. Assuming 1.0 efficiency for kinetic and HE, 50% + 200% / 2 = 125% damage per flux, while and 1.0/0.8 = 125% damage per flux if using energy.
Overall ability to fit improves by 10 OP and 300 flux (so ~40 OP worth of stats), to 10 OP and 240 Flux (so ~34 OP worth of fitting stats), so approximately 15% easier to fit and use. It gains baseline range and armor penetration over the IR Pulse Laser in that case. It's also in region of barely flux neutral on Wolf without skills/fleet buffs (i.e. 150 + 100 + 30 (flux distributor) - 30 (stabilized shield) = 250 flux vs 240). Flux Regulation then lets you also throw on an Ion cannon even for unofficered Wolves.
Another alternative to throw out there which hasn't been mentioned is to reduce the overall damage as well as an efficiency improvement. Essentially give it the 0.9a Plasma Cannon treatment, to make it more affordable for the ships that might want to mount them in braces (i.e. Eagle, Apex, etc). Drop damage to 250 and flux to 200/second (fire 2.5 seconds, 100 damage per shot, 80 flux per shot), which would make it quite comfortable on a Wolf, and perhaps result in an Apex that can actually afford to fire its primary armament. Keeping in mind, most medium mounts are not usually twice the damage of a small mount for twice the OP cost. So in going from IR Pulse Laser at 5 OP and ~150 DPS, it a bit unusual for the medium equivalent to cost exactly twice as much at 10 OP and deal twice as much damage.
Dual Light Autocannon->Heavy Autocannon: 5 OP -> 10 OP, 143 DPS -> 214 DPS (+50% DPS), 0.8->1.0 efficiency (-25%), 600 range->800 range (+33%)
Light Needler->Heavy Needler: 8 OP->15 OP, 150 DPS -> 250 DPS (+66% DPS), 0.8->0.8, 700 range->700 range
Right now:
IR Pulse Laser->Pulse Laser: 5 OP -> 10 OP, 152 DPS -> 300 DPS (+100% DPS), 0.8->1.0 efficiency (-25%), 500 range->600 range (+20%)
So if I make the assumption autocannons are in a good place right now, then compared to the autocannon track it looks like the efficiency loss of the Pulse Laser is half paying for the range (+100) and half paying for the DPS increase (an extra 50%). Problem is the DPS increase with poorer efficiency just makes it hard to fit on frigates. Like the old Plasma cannon was on cruisers and capitals. Not it is the way to go, but though it should at least be mentioned.