DPS unfortunately depends too much on outside variables. Aside from that, fundamentally you kill zeds with damage, not damage per second. Considering the game, you don't constantly fire anyway. You pick your targets (especially with shotguns, where shooting one target is almost always a waste of ammo), and you don't always wait until you're dry to reload (especially with the shotgun). The numbers you are talking about certainly exist, but they have far more dependence on circumstance than the *potential* damage that can be done with the weapons.
In general damage per second only matters on larger targets that pose a threat to your life. In these situations killing the target quickly is more important than killing it efficiently. Despite this, the tradeoff is particularly noticeable with shotguns because of penetration. Essentially, if you shoot a scrake to death with an M14 you deal the same amount of damage as you would have with the AA-12, but the difference is the M14 would not otherwise deal any more damage, but the AA-12 would due to penetration. I use this not to compare the weapons so much as to compare the playstyle differences associated with the perks.
Overall you can't look very far into the numbers, because they only represent baselines from which things evolve. The AA-12 has more DPS than the hunting shotgun, but not more damage (especially the way the AA-12 is typically used, i.e. on large targets). One may have more importance than the other in any given situation, but since modeling every situation is essentially impossible you have to compare the baseline values and use that to make inferences about the real thing. My inferences from the data are that the AA-12 is designed to be used in such a way that it doesn't capitalize on the perk bonuses as much as the other two shotguns, and that it is an inferior weapon (excluding DPS) to the other shotguns, especially given its position as a tier 3 weapon.