Nevalistis posted a few juicy details on current changes yet to be implemented in the Diablo III: Reaper of Souls beta build and revealed some of the bugs the team knows of that are planned to be addressed in an upcoming build.
Most End-game Legendary items are meant to drop from Horadric caches earned through the Bounty system. Some of these Legendaries are Act specific.
Greater Horadric Cache will be removed from completing Nephalem Rifts. The loot from Greater Horadric Cache will instead drop from the Nephalem Rift Guardian itself.
Legendary items and Set items have a small chance to drop when purchasing from Kadala (Blood Shard vendor).
Posted by Raticus79
Started up a new thread for what to do about duplicate plan drops
Nevalistis: Since it's been mentioned here already, I'd like to clarify - there is a bug with Legendary plans dropping too frequently. It will be addressed in the next patch in the Beta/PTR test. =) At this time I don't have a patch date to provide, but as we draw nearer, we will keep you informed!
01/04/2014 04:03 PMPosted by Zijar
Rift bags = yes very little to no drop rate but I have found new set items from them, so maybe if you get a drop from Rift bag in torment, I have a feeling it has a chance at being any Legendary item where as bty bags may be limited.
Nevalistis: Currently, both types of Cache bags (from Bounties and Nephalem Rifts) should have a chance to produce most Legendaries. For those obtained by completing Bounties, this also includes Legendaries that only drop in particular Acts.
That said, we'll actually be removing the caches that are acquired from completing Nephalem Rifts in the next patch. However, don't fear! The loot from these caches is just being moved to the Rift Guardian, and you'll be instead enjoying the loot-splosion when the Rift Guardian is defeated.
01/05/2014 07:49 AMPosted by Hinnyu
Rift bags not dropping legendaries has been a known and discussed issue for weeks now.
Nevalistis: As mentioned above, Legendaries should be dropping from both Bounty and Nephalem Rifts caches in the current beta build. We are making a lot of adjustments and tweaks in the next patch, but there's also some mitigating bugs that have been skewing loot acquisition in this particular portion of the Closed Beta. The Legendary plan bug above is part of it, but Legendaries (including Set items) are also supposed to have a small chance to drop when purchasing from Kadala, the Blood Shard vendor. This was always the intent, it just had yet to be implemented. -- source[/bluepost]