Leave the legendary items on the ground, don't pick them up.
I don't know if this is just a coincidence or not, but I think the game only counts your guaranteed Legendary/Set drops after a few hours of play with no items IF you pick the item up. I have been testing this out by leaving the Legendaries on the ground if its been a while since I haven't gotten any, and I seem to be getting a ton more immediately after if I never pick them up.
I know many people will play and get nothing, and then all the sudden they may get two or something at the same time.
Can anyone else test this to see if this is correct and not just some lucky RNG that I'm having here?
Note it only seems to work when you are in the "guaranteed" Legendary mode after not getting any for hours. Either I am having really good luck here, or I may have found something....