Rolling individual Bursts or Spreads would be unthinkable with big dice pools. High level builds could be rolling 15+ dice. Imagine rolling 15 Spreads for 1 attack.
Yes, at level 1 with un-mod-ed equipment, it all works smoothly. Damage Effects only go crazy when the dice go up.
Consider a Muzzled Quick High Capacity Recoil Compensated Automatic Combat Shotgun with Commando 2, Quick Hands and Shotgun Surgeon (Damage 4+2, Fire Rate 7x2, Burst, Piercing 1, Vicious), against a big group of things with 10 physical DR on every Hit Location. The 20 Damage Dice will roll an average 16 damage and 6 Effects.
EDIT: Oops. Automatic Combat Shotgun doesn’t have Vicious. Calibrated Combat Shotgun has Vicious, but no Burst. So, these numbers aren’t for a real weapon, but show how these Damage Effects can add up.
First Target = 16 + 6 Vicious - (10 DR - 6 Piercing) + 6 Spreads × [([16 + 6 Vicious] ÷ 2) - (10 DR - 6 Piercing)]
= 18 + 42 Spread
= 60 HP loss to first target
6 Bursts with Spread = 6 x 60 = 360
6 Bursts no Spread = 6 x18 = 108
One-shot-ing a Mirelurk Queen and her 6 friends. With one attack. With a build available with level 6 Perks.
Now without any stacking:
First Target = 16 + 6 Vicious - (10 DR - 6 Piercing) + 6 Spreads x [( ÷ 2) - 10 DR]
= 18 + 0 Spread
= 18 HP loss to first target
6 Bursts no Spread = 6 x (16 - 10 DR) = 36
This still does enough damage to inflict Injures on all 7 human-sized targets, but doesn’t break the game.
I’ve seen it suggested to apply Piercing to Spread, but not Vicious to Spread. But, for me, a Scattergun Laser Rifle with Laser Commander 2, Mister Sandman, Rifleman 2 and using the Accurate Quality does crazy stuff.