Golden Key rewards: How do they work?

I assume that golden keys have some minimum quality level but not sure what it is. I had erroneously thought you would get 1 legendary but after opening one finally that proved untrue. Does anyone know how the keys work with regard to the rewards? Is epic the minimum quality you can get? What is the chance for a legendary?

Also, as a side note…is there any reason to hold onto these keys until later (like after DLC is released)? I know waiting until 50 is a good idea but not sure if I should just save these until later or not.

I’ve never seen a posted description of odds, etc but I consistently get purples. 4 keys and no legendaries - have seen a reddit post where someone had a white…not sure though.

I have gotten 3 purples 1 blue.

All purples.

All legendary.

Half legendary half purple.

It is random, but typically good quality.

Yeah, I know it’s random but they clearly have a higher minimum quality level than a standard red chest so I was just curious if anyone had an idea of the parameters. I was also curious if anyone was saving them for later (for DLC content or something).

Good to know they can drop as low as blue…that sort of sucks actually. That kind of diminishes the value IMO.