Fun Time Sink: Walking on a map, navigate space, because it introduces movement speed / leap / teleportation game mechanics. Travelling isn't really a pain because you slay monsters along the way.
Pointless Time Sink: Game being paused to hear Boss dialogues you've heard a hundred times before, you know you'd click the "Skip" button. If you've assigned a shortcut key for "Close All Windows" and use it to skip dialogs, you know that the dialogs are pointless. SOLUTION: Add a checkmark below the Skip Button called "Automatically skip future dialogs."
Fun Time Sink: Events with nice rewards, and free NV stacks. If you're pursuing a boss, you'd still be willing to pause and take time to finish events. Events that are like party games are great! Jar of Souls? Who would resist that?
Pointless Time Sink: Crafting Gems Take 5 seconds each. We've seen that it could be done for 0 seconds in Diablo 2. For those who think that this is introduced because of the AH: Sorry, Blizzard has been clear that they will Not balance a game around the AH. SOLUTION: Just remove the delay. Gold cost is still ok. The delay is fake and pointless.
Fun Time Sink: Challenging Elites. The ones that really contribute to the time sink factor are the Extra Health and Shielding. It introduces a mechanic that encourages players to get high DPS, as well as decent defense.
Pointless Time Sink: ID'ing Rares. One by One. With a delay. We all know that rare items are 99% going to be crap. Getting that Trifecta Gloves is like winning a lottery. So many trashy affixes to ruin your chances of getting an item that is useful for your hero, and here we are faced with the fake excitement mechanic of UnID'ing items for 1 second each. SOLUTION: Remove the delay, Allow ID All just like in D2.
Fun Time Sink: Farming for the Hellfire Ring. You'll farm for keys. You'll farm for organs. And then you craft. Repeat, rinse. It doesn't get old, the quest to get that perfecta or quadrifecta Hellfire Ring! It encourages players to get more powerful gear to be able to handle higher MP levels, where the drops of keys and organs have a high chance.
How about you? What are the Fun and the Pointless Time Sink you find in the game?