I've killed the Warden in Act III literally 10 times in a row with 5 stacks, and 475% gold find on MP4. No key. I'm ready to throw my computer out the window.
Dude I feel you. And the answer "go higher MP" would annoy me too as im sure it does you as you obviously would if you could handle it. I was having some bad key runs. I reccomend just doing some regular act runs and grab some legendaries to boost your diablo drive.
5 Keys in a row on MP4, stopping by the warden at the end of my runs "just cuz". Although, I have never found an item worth more than 10m in almost 300 hours of playing. Win some, lose some I guess. :/