Pinning fire is only available on two weapons: the shredder autopistol and the boltgun.
The shredder autopistol performs well but also has significant weaknesses: effective range and carapace armor.
The gun is pretty much garbage without pinning fire. Nerfing pinning fire on this weapon, would require a comparable buff to the weapon’s base stats to compensate.
The gun is not overused at all, so imo no sign of overperformance.
Regarding Pinning Fire on the boltgun:
TLDR:
Nerfing the blessing to nerf the gun’s peak performance, ok (gun might overperform a bit; it has basically no weakness aside from low ready speed and reload speed).
Nerfing the blessing to increase build diversity, pointless.
If pinning fire is nerfed into the ground, nobody uses it anymore (and everyone uses one of the 2 defensive blessings instead)
If pinning fire is not nerfed into the ground, everyone will still use it because it will still be one of the top 2 options to increase damage
Long explanation regarding boltgun:
Unless the blessing is nerfed so hard into the ground that it does effectively nothing, nerfing it, will not change anything in regard to which blessings are picked.
Why?
The Boltgun has access to the following blessings that increase damage output:
Pinning fire (power from staggering)
Cavalcade (crit build up while firing)
Surgical (builds crit stacks while aiming, uses them on next shot)
Shattering impact (brittleness)
Surgical is a garbage blessing for any weapon that shoots fast, and should only be available for stuff like helbore lasguns (long range weapons with charged shots or low firerate).
This means that the Boltgun effectively has 3 blessings that increase the damage output.
Cavalcade T4 stacks up to +20% cc (5x 4%). The boltgun has a crit multiplier of around 1.3x. A 20% extra chance to deal ~30% extra damage is an average dmg increase of ~ 6% (0.2 x 0.3 = 0.06) once the blessing is fully stacked up.
As long as there are no special interactions with critical hits, the extra damage is all that they do.
This leaves only two blessings and therefore one choice, if you want to build your boltgun for max damage: Pinning fire and Shattering impact.
Even if pinning fire was nerfed by a lot, it would likely still be a top pick for the boltgun.
Until it is nerfed so hard that it has effectively no value at all, where it would not be picked at all anymore, and likely be replaced with Inspiring barrage or Gloryhunter.
All of that said, i think that there should be no more significant balance changes made in the game, until we have the option to upgrade our item modifiers to 100% as well as having free choice to swap both perks and both blessings.