While I understand your approach, just to give my two cents on each champion:
Olaf: His recent buff did him justice, with jarvan and anivia not really played he can just pop ult and hundred to zero the enemy adc (unless it's Kalista...) pretty quickly with the right build. With that said it requires your team to follow up and record summoner spell times otherwise you'll die miserably when they flash and suddenly its a 4v5 that your team probably can't win.
Twitch: I actually cant think of why you listed him, what's wrong with him currently? I'd be more eager to put up Miss Fortune than twitch... I think he's in an ok spot atm: just has to suffer through difficult laning phase with all the leonas and naut's in solo queue currently.
Jax: I agree with slightly. I dont think he's that underpowered it's just solo queue tends to end before he hits his stride: and if he falls behind... well it takes a long time to become the monster jax is. Still love the champ, but wouldn't mind him seeing a little love.
Dr. Mundo: I LOVE MUNDO!!!!! HE'S SO FUN!!!! Anyway, the only problem I have with mundo is again team keeping track of summoner spells, since ignite does work on him. Otherwise he can q farm (or if they try to deny, jungler can gank when they deny since already slowed) if he has to, and when the waves are ~even he can all in post six very easily since most tops run tp. Also a turret diving monster.
Elise: People pretty much covered this one, I don't even know what she is anymore: ap fighter offtank? mage? I really have no idea.
Syndra: She was popular for so long, the nerfs might have been a liiiiittle too hard, but she was buggy for awhile after them which is probably why her winrate went down (I didnt go back to her after the bugs anyway, figure other syndra players felt similarly)
Kha: I can't really have an opinion on this one either... I don't play him enough, sorry D:
Miss Fortune: juuuuuust adding this one~ I thought of adding quinn but MF needs some love...