Mf relies on things that are not in her control to function
In lane, you need enemies positioning/minion positioning/your positioning to use your Q, and thats not even 100% guaranteed because I cant even count how many times the second Q has gone to the minion who is just a pixel behind him, instead of the champion that you are actually aiming to.
She doesnt work with half of the supports because she needs someone that can secure her a kill, because she lacks CC and Chase potential (your passive is useless to chase people, even if W can refresh it)
On Team fights she needs someone to lock down multiples enemies so she get a full effect of her ult for 2 segs, on top of that she also needs the enemies to position themself in such way that she can hit more that 2 people, AND she also needs to position her self in such way that no CC will interrupt her casting + can actually hit people for the full effect. And even when those conditions are meet, the effect is meh at best.
I went from 0 champ points to 22k champ points since her "rework". Every lane I won was because the enemies didnt know how MF worked and stayed close to almost dead minions which allowed me to poke and zone them. The only times I killed them was when my support was able to pick someone.
Honestly, she is strong. Her numbers are strong, her kit is strong. She IS strong.
But I wouldn't play her other than normals. If I want to win, I need to make sure my winning potential is not tied to so many factors that I cant barely influence.
Honestly. Her Q needs a buff. Either increase the range (Since you nerfed the cone without any compensation) or make it prioritize champs when you kill a minion.
Her W needs some work too. Make it work like teemo's W, where when he activates the W the MS bonus is increased and cannot be stop by dmg. Give some indication for her W passive stacks (talk about hidden power).
Her E should be fine if you do any of the above in terms of numbers. But it needs to be insta casted (why can Jinx insta cast a snare (with a 0.7 prep time ofc) but MF has to stand like an idiot to cast a simple slow) and also reduce the mana cost on her E (it cost 80 mana while Jinx E costs 50 wtf)
Her ult does meh dmg, especially on late game. If it had an actual AD scaling it would be great. Make it work like Lucian, that could fix some problems.
EDIT: Also you said MF passive was going to have scaling per level. You liars, it's not there, it was never there. You nerfed MF and called a rework and lied to us about it.