Well you're not alone, I farmed for quite some time for keys, and got zero, and 1 purple. I am not going to complain as it's the nature of RNG, there is little point raging about something you have utterly no control over. I had fun doing it, patrol was pretty lively for once, and Skyshock when the enemies move against one another is nuts. There was little point me farming so much as the keys are more relevant for the higher level PoE, which I don't have a team for( I knew it was the case with the keys before I started farming ) but it would've been nice to have 1-2 in case I got an invite to one.