Well to be honest there is no difference. In both cases the over-geared person gets a piece of loot that is a downgrade for them. The over-geared person is getting one of the drops of the boss. The same drop that could be an upgrade for someone else.
And in both cases the over-geared person is there for the reason of getting those items for whatever reason. Again, taking one of those pieces of loot. In both cases they are taking a piece of loot off the boss.
The only difference is the perception of them pressing need. In both examples you gave the over-geared person is taking a piece of loot that they dont necessarily need off the boss, instead of it going to a player that it would be an upgrade for.
In the examples you gave, with personal loot, they would have to offer it for roll if they didnt want it, or just trade it to someone. With group loot they have the option to press greed or pass.
Yes it did. In every raid with PL you were competing with every other member in the raid for a piece of loot off the boss. Class, spec, ilvl of the player didnt matter. In PL you were rolling against everyone in the raid. In PL the boss died and every member rolled dice. The highest rolls got a random piece of loot for their spec. In group loot, you are competing with only those members of the raid that can also use that piece of loot.
The issue with group loot is that you actually see yourself losing the roll. And losing feels bad. And that is why people get mad.