When Diablo 3 first came out, the World of Warcraft essentially died as a huge number of players migrated to the latest fad. Although there still is a fair number of people playing D3, I think that the initial mass rush is over and people are slowly returning to WoW. The fact that the queue times aren’t as bad as the first week or two of D3’s release and the increased success rate are indicative of my theory.
That said, LFR still suffers from terrible players so it’s important to note when the best times to queue are. My feeling is that the best times are on week nights minus Fridays for LFR part 2. Mondays might be the best day as it seems that the vast majority of players hit LFR right after the resets. Unfortunately, you will have to suffer through the large number of immature asshats, but there’s a good chance that you’ll avoid ridiculous wipe fests along the way.
Saturday during the day seems to also be a reasonable period. However, I found that Sunday is pretty awful although at night it might get better. My guess is that the average person who might attempt to queue during the bad periods tend to be quite clueless. Also, I think that most people who wait to the last minute are these average players who get in just to see what it’s like. The biggest frustration comes more from the last two parts of LFR part 2. But if you see your group downing Ultraxion within a reasonable period, there’s a good likelihood that your group will not fail with regards to straight DPS.