Tldr: IR Pulse is acceptable, but worse than other options, vs frigates and very bad against anything larger.
The issue is that while dual autocannons are bad against armor, and light assault guns are bad against shields, IR Pulse is 'meh' against shields, 'meh' against frigate armor, and 'really bad' against destroyer+ armor. It has no strong points.
The "standard" comparison would be 1 dual autocannon and 1 light assault gun vs 2 IR Pulse. 303 flux for ballistics, 304 flux for IR pulse, so same power draw. Against shields, it is 366 DPS vs 304 DPS. Not terrible for IR Pulse, but 20% less.
For armor, lets say 250: less than a Lasher, more than Wolf. The ballistic is doing 320*80/(80+250) + 71.5*25/(25+250) ~ 84 at full armor, 138 at half armor. The energy is doing 304*50/(250+50) ~ 51 at full armor, 87 at half armor.
In both cases, the IR Pulse are outclassed by a significant margin. Against armor in particular it is no contest, and this is frigate armor: the heavier the armor, the worse it gets until both are at the minimum damage threshold, where its something like 39 for ballistics vs 30 for energy, which is still bad for energy. The IR Pulse encounters this limit at 500 armor and above, while the ballistics encounter it at 800 and above (the kinetic at 250, but it is the minority contributor).
In addition to longer range, the ballistic also has the option of switching weapon groups on or off to improve efficiency: they can "overgun" the ship and attempt to run kinetics vs shields and HE vs armor. It doesn't always work as the AI is decent at shield flickering, but in general a player can reduce their flux usage by managing weapon groups vs appropriate targets. The IR Pulse cannot do that, so suffers by comparison in efficiency.
Now, granted, light dual autocannons are horribly innacurate, and against nimble frigate targets can and will miss shots. But the light dual autocannon is a notoriously "meh" gun: its the Railgun that the IR Pulse really has to compete with, and Railguns are hilariously good. So good, in fact, that the Pirate Shrike is considered by a lot of players to be better than the normal shrike because it can mount one, despite also losing OP.
...
If IR Pulse is bad, all energy weapons with low shot damage are bad.
...
Honestly, yes: All energy weapons with low shot damage compared to their target's armor are bad
unless they have some special factor. Pulse lasers have the special factor of DPS, coming in at 303 as opposed to the 214 of heavy autocannons, and their 100 damage per shot makes them acceptable against destroyer grade (~500) armor with the increased DPS taken into account. Vs destroyers, Pulse Lasers are good guns. Vs cruisers they struggle and vs capitals they are defeated by armor. Autopulse at 150 damage are a little weak vs cruiser grade armor, but they have a very strong alpha and good efficiency as bonuses. Plasma Cannons have enough damage per shot that, despite being 'scaled up pulse lasers' they remain great against every target.