It has happened time and time again. Numerous huge threads pop up every time a major patch comes out of people who find 100 times more Legendary drops then they normally would given the amount of time they played.
Currently the AH is OVERFLOWING with amazing gear. The only problem is that the BOTS are inflating the prices so high that only gold buyers could possible afford any of it. It is my personal belief that the AH being supersaturated with good gear is causing less good gear to drop.
Not very long ago Legendary items were dropping at a very high rate, but they were all horrible items. Now it seems like even those are drying up.
Something is definitely fishy here. Blizzard is seriously adjusting variables in real time to try to experiment with the economy. This is all just a big test for them, we are the guinea pigs.
I think their biggest concern right now is testing, experimenting, tuning, and flat out punishing players via their hidden drop NERFS. Why? Simple their next MMO will incorporate a monthly fee AND will have a RMAH AH.
Diablo 3 is nothing more then a test run in unexplored economic gaming territory. If you buy gold on RMAH you are supporting a future of pay 2 win games, instead of play for fun games...
As soon as the Paragon system came out Legendary items were dropping left and right. As I've leveled up I have gotten less Legendary items per paragon level. This makes absolutely no sense statistically as my magic find % has increased, and you need more XP per level...
Another possibility is that if you use the RMAH you gain boosts to your drop rates, or perhaps if you don't ever use RMAH and reach a certain level of uberness they NERF the heck out of your drops?
I am 99.9% sure that if there was a global chart which showed the average Legendary drops for players/time played it would spike very sharply around the time of a new patch and over time would gradually decrease.
Of course it is impossible to isolate this phenomena without data only accessible by Blizzard, but I know for a fact something is wrong. And this does not necessarily mean that it is even intentional. Honestly given the state of this game it may be more likely that the whole system is actually just filled with unintentional bugs which their poor programmers are unable to identify due to Blizzard not giving them full access to all the necessary data.