Dummy testing with the beam staff seems to show the primary (beam) fire starts by dealing rapid but tiny ticks of damage to enemies, with the ticks becoming much stronger and slightly slower with every consecutive hit on an enemy, resetting on any miss. This isn’t subtle either, the first tick of my staff does a measly 75 damage but builds to 975/tick if held on target. Clearly you are meant to hold the beam on targets instead of sweeping it about or whatnot. This also effects the beam-blast alt fire (right click during left click), the more consecutive ticks you hit an enemy with before triggering it the more damage it does to a major degree.
This causes problems with headshots, however, because essentially all non-boss enemies flinch when hit in the head. This flinching animation almost always moves the enemy’s head enough that at least one of your damage ticks misses, causing the damage buildup to reset back to zero. You can’t follow the flinch animation either, because it re-triggers every single time the staff deals damage with no “cooldown”, causing the enemy to spastically start and re-start their flinch animation over and over rapidly and keeping their head moving in an impossibly jerky manner. This is easily demonstrated on the target dummies as they flail about every time they are hit. Try to hold the beam on their head and you will find it impossible, the flinch animation makes you miss and resets your damage continuously.
Because of this, you deal more damage not aiming for the head with the beam staff against most enemies. No matter how i try i cannot get the staff to tick for more than 925 damage when targeting dummy heads because the consecutive-hit-counter keeps getting reset by the flinch. Remember it ticked up to 975 damage with consecutive body hits. I get the same results with the beam alt fire (not the shotgun), no matter how i aim i cannot get headshots with the alt fire to deal as much damage as body shots because i can’t build consecutive ticks on heads.
Given that the beam staff is labeled “sniper” and the game encourages headshots massively, this seems pretty wrong.