So I have been searching for this information but all the stuff I find is related to old Diablo in regards to monster power and Nephalem valor. So my question is, do the Keywardens always spawn? and What is the drop rate for the keys. ( also on a side note if anyone knows the drop rate for the Staff of Herding plan).
Keywardens always spawn. They only drop keys on T1+. Last I heard was that droprate for keys was between 25%-50% depending on what torment level you are on, same with organs.
Key of bones = Field of Misery
Key of Gluttony = Oasis
Key of War = Stonefort
Key of Evil = Silver Spire level 1
Also I have seen keywardens occasionally drop a second key, usually a different type. For example I've seen the stonefort warden drop a key of war and a key of gluttony at the same time, though i've only seen this above torment 3
In general that chart is great, and correct regarding keys, but lots of information in that chart is outdated... haven't found an updated version of that yet, unfortunately. Therefore, be careful and don't take everything in that chart for granted ;-)