Maybe it was different for D2, but I found the random class loot to be a huge issue in D3 since it seemed designed to force players into using the auction house. Once the auction house was used you could easily get gear far surpassing what you would find naturally, which turned all loot collecting into a number crunch for getting ingame currency. Even if you only share to your other characters it makes those runs easier in a game that was already very easy at start, which doesn't help when figuring out that class's limits. D2 had a much higher baseline difficulty than D3, so getting high end gear from your other characters might have made a lot more sense there.