One of the problems I have with quests is that they tend to inhibit grouping. People generally don't feel inclined to run around helping other people out on their quests if they aren't getting rewarded themselves. And when there are 5000+ quests in the game, its sometimes hard to find people who are on the same quest as you. In EverQuest II, this problem is exacerbated by the fact that many of the quests involve multiple steps (some individual quest steps in EverQuest II would be entire quest chains in their own right if they had been implemented in World of Warcraft.)
Sharing quests is a hackish way to work around this, but it doesn't work too well, since all it really does is remove the need to find the quest giver.
The most reliable way to find groups in EQ2 is to not bother with your quests; if you go on an instance run instead, there are far more people inclined to help. That's because they get something out of it too.
What if the game were designed such that all group members get some small reward (XP, AA, and/or faction) every time a group member advances in their quest (both by helping them advance one step, as well as bringing a quest to the (Completed) state)? If that were the case, I think more people would be inclined to get together simply to help each other knock off updates.
No existing MMORPG could add this type of feature, since they weren't designed around it. However, if future MMORPGs are going to continue utilizing quests as the primary means of advancement, this issue is something they are going to have to address.