Excellent Thread Indeed! Sometimes, on the world wide web, we forget that there are different regions having different traditions and different hunting conditions. One can ask the same questions to hunters in shot-gun-only states, western states, and the southern tier of states....and all answers will be based on the region.
So....when shotguning for deer comes up....you will get a broad set of answers.
I will address deer hunting with shotguns in the southern tier of states. Shotguns, buckshot, and dog hunting has a long tradition in that area. Not that rifles were not allowed, but rather based on thicker woodland cover. In the Southern hammocks, swamps, and coastal islands....a shot over 50 yards is rare and most are much closer.
There has been and is....a very large number of buckshot hunters you seldom hear about! Not much has been done for them at the ammo factories and the syndicated rag writers are not concerned. The experienced buckshot hunter knows his range limitations!
Dixie Tri-Ball was mentioned and it is a fact that the load is the most powerful buckshot made......fact! It spans the use of buckshot and slugs in all-gun-states. It has been proved very effective on real wild hogs!
Now....We are seeing another change happening in this Southern tier......shotgun hunters buying rifled barrels for their favorite shotgun! A shotgun with a rifled barrel becomes a large bore rifle on a shotgun frame and can be the finest brush gun going! Hunters in this area want a switch barrel gun....not a dedicated slug gun.
I think we should think more about regoinal attitudes when we discuss shotgunning deer. Just because it may not be used in your area, whatever the reason, it is a viable method with the correct equipment!