I have a few suggestions that would really help out the function of the LFG tool.
1) Give a bonus that rewards a loot bag from the undaunted that stacks to 7. This will be nice for those who can only play on weekends and encourage people to use the LFG tool more often.
2) Make the LFG tool queue you for a random dungeon. This will eliminate long queues if you happen to use the LFG tool and have a dungeon selected that nobody is running.
3) Make the LFG tool cross faction! The way it is now is just bad. Essentially you are limiting the players to 1/3rd of the player base, and even less since you don't know what dungeon anyone else is queuing for!
4) Give increase to experience and gold drops while running a dungeon if they used the LFG tool. I would also increase the drop rates of rare ingredients and other crafting materials while running dungeons using the LFG tool.
That is about it. Opening up the factions and making the LFG tool queue you for a random dungeon would speed up the time it takes to find a group and with the addition of the stacking bonuses and increase to exp, gold, and mats the LFG tool would flourish. Not only that but communities would boom, new friends and possible alliances would be make.
PS: Random dungeons would work amazingly now due to dungeon scaling. That was the only issue that was holding me back from making this suggestion a long time ago.
Just my .02 cents if anyone else has a suggestion feel free to add it in the comments!