I have a legitimate question about Diana.

I have recently noticed a trend in the games that I choose Diana as jungler: I LOSE THEM ALL. Now yes, I am obviously not even close to the best jungler out there, and I fully recognize that. However, the thing is, I DO win a large majority of my games as other junglers, such as Eve or Poppy. It's not that I'm bad with Diana, my scores aren't HORRIFIC, but there's definitely something... Is Diana even a viable jungler anymore? Should I even bother trying to master her or just go ahead and use some of the better junglers, like Vi or Lee Sin? I never even see her used anymore, so I assume she can't be that good, however I really like her and want to master her. I have had her for quite some time, and I understand that, once again, I'm not that good at jungling. But the fact that I never win games with her tells me its more than just my skill, considering that I used to use her all the time. Honestly, is she viable or not?