I think the most egregious example of overly mechanical champs in that bunch would be Yasuo.
I don't think he's OP, he just has such complicated and stuffed kits that it makes really confusing problems. Poor Yasuo has such a cool concept, but a few things are just... unnecessary. I mean, think of how much of his power budget could be put towards numbers and scalings if he didn't have double crit, if Flow was an actual resource he had to manage, if his ult didn't give him armor pen, etc. (That last one bugs me the most; it's counter intuitive that the super-cool shrieking anime-dunk doesn't do the killing damage, it just sets up him cleaning up kills with autos and basic abilities.)
Besides the fact that it's hard to balance right, it also sucks for new players going against him. God I remember the first twenty times I faced him as a mage, it felt like 90% of the time I literally couldn't touch him with skill shots. He either wind walled it, dashed to a minion to dodge, and if he can't actually outplay me, don't worry, he gets a Get Out of Jail Flow. Meanwhile, I've been blowing mana on trying to damage a manaless champion. That never ends well.
Now I know how to bait out stuff like that, and he really isn't a huge problem in lane anymore (no more than any AD assassin) but I distinctly remember being on the verge of quitting league because I felt like he was literally invincible against mages.
Speaking of mages!
I started league a long time ago, playing old xerath as my main. Never really was big on league, kind of lost interest. Wasn't that fun, always got my ass beat, lost contact with the friends that played it.
Flash forward to march 2014. I'm in college, meet a lot of new people, turns out they play league. I get back into it, see a tentacle mage monster is on free week, try him out.
Instantly fell in love, been maining him ever since. Vel'Koz is why I'm playing league today. I'm really not in any place to make an objective analysis on him because of that, but holy shit I love Vel'Koz so much for so many reasons I could rant about forever. Really though, looking back, it's nice how simple he was to pick up as a new player.
Passive, land three spells for bonus damage.
Q, shoots straight, splits in two. Can detonate early. Slows.
W, shoots straight, does damage twice. Highest damage, no CC.
E, ground-target, knock up.
R, go Alderaan on their asses. Slows.
It took only a few games to understand what his combos were and why. "Oh, I never lead with W; use Q or E to set it up with CC, and complete the passive stack. Makes sense." "Oh, wow, shouldn't use the E as initiation most of the time, since it's my only real defense." "Oh wow, I'm pretty defenseless while ulting, better choose when and where I use it carefully."
All of the complexity and learning wasn't memorizing a laundry list of mechanics and debuffs; it was emergent, resulting from some very simple abilities. I like seeing this in champs, and I think it happens more often than not. Really, I think Yasuo and Kalista are the only overly mechanical champions you listed.
Well that turned into a long post.