I vote for Diana. Assassins have made their way back into the meta and Diana can be a very rewarding champion to play if you get some practice with her.
Tho, a lot of matchups in mid can be hell for her (depending on how good the opponent is) and until the lvl 6-9 you wont have a fun time against something like Zed or Yasuo.
As for jungle, after hitting lvl 6 you can snowball the entire game if you catch the enemy botlane a couple of times with a follow up of getting drake.