In Diablo2/LOD, Boss runs were fun for 2 reason.
1-They were fast
2-They had a nice drop rate for unique and rare
I remember when I ran Boss runs in D2, it wasn't getting the best items which was fun. It was getting a unidentified item which could be a variety of unique items. If you got a unique ring, it could have been at least 12 different kind of unique rings. That sensation and hype of getting an item was very fun part of Diablo. Not to mention, these runs were fast. This mean you can get on for 30 minute and do at least 15 runs before stopping.
At the moment, there is nothing like that in Diablo 3. If I want to run, I have to go out and look for bosses. It's not an issue, but it is time consuming. The fight themselves are just as long, some taking forever in inferno. It also gets very frustrating getting killing in one hit DESPITE having a decent gear. As far as drops go, even if a unique/legendary drops, It's of a YES, but I know I wont need it. I fond only 3 legendary in play play-through to inferno act3. I have no motivation to look for any more of these items because they aren't rewards or satisfying after I get it.
Also, boss run(Diablo, Balial, Azm )should still have okay drop rate. Instead, after fighting in for 20+ minutes, Im rewarding with nothing but blue.