I don't know if this help counting the odds, but this is what happened to me couple days ago.
I was doing agrus quests on my DK, and while i was completing smaller invasion the end boss dropped legendary blood pants (Rattlegore Bone Legplates). I was like, cool.. I'll just finish these quests and go and get me some 910 ring to replace frost legendary ring I was using so I could equip those pants.
Couldn't be more than half an hour later when I was at the relinquished vendor ready to buy a ring, and !bam! legendary blood ring (Lana'thel's Lament).