I've also noticed that when you end up in a competent PUG these days it tends to last longer - you're not getting people grouping for one quest and then leaving. Just last night, my friend and I picked up 3 solid PUGs (one who was solo and another duo) to run Irestone Inlet. A half dozen or so quests later, we finally disbanded.

If groups last longer once they form, it would stand to reason that there would be fewer lfms from the same number of people.