I always thought that the original group finder for WoW was the best, you could sign up for LFM or LFG, but it wouldn't just slide you into a party on it's own. You still needed a party leader, which is good because there is no system to having a dungeon leader in the current LFD tool. When it's in the hands of a player to form the group, they will put forth a little more effort during the actual run, marking targets to trap/sleep, ensuring all members of the group know the fights, etc. The people looking for a group are encouraged to play nice with PUGs, because if they have a poor image, party leaders will quickly make sure to never invite that person to future dungeon runs. While these cross server groups make it a bit faster to get your dungeon going, I would much prefer a tool that actually encourages players to socialize with others over a tool that just gets you to your destination as fast as possible. If I needed instant action like that, I would play a game like Torchlight.