The only people who use this weapon are newbies that are using it as a crutch. For this reason, I think the weapon deserves some looking into.
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Problem 1) Pulsars are awful to play alongside in PvE
Say you're about to attack something and the bullet is coming. It may or may not knock the thing back based on if it's big or small when it hits and whether it freezes or shocks. You have to predict the impossible to land your attack, while the pulsar user.... spams attack.
Problem 2) Pulsars don't do enough damage; they deal the same as valiance lines on their expanded shot
This is good for LD where the weapon is over powered but bad for PvE where the weapon is kind of under powered. Ergo there isn't much of a solution available.
Problem 3) It's still fairly op in lockdown
I'm not an expert here but that seems to be the consensus.
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Solution 1) Remove pulsar knockback entirely; make bullets penetrate their targets + deal the same damage regardless of size
This would keep the gun as similar to the current as possible while making it play better.
Solution 2) Make the shots an entity like mixmaster bullets, and have them do something weird like slow down as they travel
This way, enemies won't be triggered by its shots, and you can use it to fight say, devilites, beasts, stuff like that.
Solution 3) Weaken the main attack and buff the charge attack by making that grow to be absolutely enormous.
More of a charge centric gun would fix the LD issues, as well as breathe new life into the weapon
They're fine at what they do now, with your "solutions" you wanna just remove their main role which is keeping crowds at bay. If you want a charge-centric no-knockback gun go for a catalyzer. However that doesn't mean that pulsars aren't overpowered, I suggest that they get the attack speed of alchemers rather than blasters, that would make them less spammy and annoying in parties and lockdown.