Either they improved their tech by a huge amount, or not as many people are playing. Logically, it is probably a combination of the two.
One can't say either way since we have nothing but anecdotal data - but it would seem that if the game had as many people as WoD, instead of 4 hour queue times, the most popular servers would at least have seen maybe a 10-15 minute queue time? Zero queue times does get a bit suspicious in terms of actual number of people playing.