Again, sorry for not reading the whole thread, but well, coming so late into the discussion only to find 51 pages is a bit overwhelming.
It is true that killing the same boss repeatedly ad infinitum would become boring and tiresome.
But generally speaking, bosses are slightly trickier than normal enemies to fight and kill, so repeatedly farming only the same area with generic monsters would get old as well.
Personally I think it’s a matter of preference, I would pretty much grind experience on hordes of mobs to enjoy some good old carnage, and run some bosses for items (since they generally drop more interesting stuff).
One thing for sure is that the approach that Blizzard took with Diablo 3 is fundamentally broken.
Once reached the level cap you need to waste a lot of time looking for rare pack of monsters (usually much, much more stronger than bosses), kill them to get a timed buff, stack said buff a certain amount of times and then go to a boss. The buff would ensure better drop from the boss.
This is not exactly bad per se, but as it is you actually have no other choice if you want to find some higher level rare items. And the fact that this rare mobs are actually very frustrating to manage and kill, combined to the ridiculous amount of money you need to spend to repair the equip every time you die, combined again with the fact that most of the drop are subpar even for the zone you drop them has created a super negative combo.
At least it was this way when I stopped playing because it had become a chore, more than something to have fun with.
All this digression, was not just to bash Diablo 3, but to say that you shouldn’t try to remove options from the players. Otherwise you’ll end up in a spiral of bizarre shenanigans to force them to play the game the way YOU want, instead as the way THEY want.
People like to farm bosses? Then don’t penalize them with ridiculously lame drops to force them to look for random rare monsters.
People like to farm monsters? Then don’t penalize them by making such monsters a combo-nightmare of hellish random abilities.
EDIT:
To add that probably the part of the game where farming would become a serious thing to worry about is when you reach the level cap and you have already explored every nook and cranny of the game.
At that point your only worry could be to find new and stronger gear and probably you’ll end up farming the same boss(es) all over again.
Path of Exile’s developer created something interesting to add a little spice to the end game.
Monsters can drop random items called maps. By using a map you open up a set amount of portals that transport you in a randomly generated dungeon with different characteristics (based on the scroll prefixes and suffixes). The dungeon would contain not only one or more bosses (or minor bosses), but even normal monsters and once the inventory fills up and you want to get to a vendor, one of the portals will be consumed, so you have a limited amount of chance to get in and out of the portal.
This mechanic seems quite interesting and could be very useful to keep a good level of entertainment once you reach the so called end game.