Conditional does extra damage from the ignition or shatter so that is why. It is also an aggressive shotgun so it does more damage. It can even shotgun melee some of the lower dr supers
If I remember: Bubble and Well die to shotguns pretty much with no extra issue,
Storm Edge and Behemoth are resistant and basically need every pellet to land but will die in one hit,
pretty much every roaming super except I believe Arc Staff, Burning maul, and Dawnblade die to 1 shotgun + one melee as long as enough pellets hit and you're in range.
Also depends on the shotgun type, overshield versus no overshield, and other dr sources but at a base you're right.