Miss Fortune is actually pretty good right now...
...in lane. Her lane phase is pretty sweet, I really like the bonus damage on Q when it kills a minion first. It's satisfying and skill-based. Excellent work on that. The lack of grievous wounds isn't QUITE as big a deal as I had anticipated, but then I rarely play against Mundos, Volibears, or sustain supports. So whatever. I can more or less agree with why that was removed. And the Make It Rain change actually makes it a very noticeable skill early on, finally giving just the right amount of utility needed to set up longer trades in lane.
Unfortunately, games have a tendency to almost always reach late game in the current meta, which means big tanks and hypercarries to kill them, with MF being neither of those. Worse, while she can absolutely pummel an adc into the dirt in lane, most popular carries scale so much harder that with some time to farm or even just a kill or two in some cases (jinx and vayne come to mind), her dueling potential goes right down the drain, even if she had a huge lead before.
What I find most problematic about this is that the entire purpose of picking a lane bully is to shut down late-game scalers early. Now, I'm NOT complaining about the scaling of those other champions, I like what they do and that's fine. Don't touch that. But my issue is, you have an item-dependent carry who really doesn't scale outside of lane. At least not to the degree of nearly any other adc. More specifically, her ultimate is so pathetic in terms of scaling and practical usability that it is pretty much obsolete by the time you get your second point in it. Even when you first get it, chances are you will only ever use it for executing targets who have escaped outside of your auto range, and even then you will only get maybe 3 ticks on them, which is only enough to kill them if you could have killed them with another auto or so. It just doesn't feel nearly strong enough for an Ultimate ability.
So let's look at why it's such a weak ability. For starters, it's a channeled AoE that can be avoided or interrupted. It takes time to get the full effect of it, which enemies can just walk out of. Additionally, a team fight can be decided during the duration of the channel, by which point one or two of your allies has likely been killed or mostly killed by the enemy adc already because they have been autoattacking.
Bullet Time has nearly zero upfront damage, really nothing even noticeable beyond the low healthpools of laning phase. It's only AD scaling is on its stacks, which, ok, if you want to make it a mark-and-follow-up routine, that could work... EXCEPT that it's an aoe, and is balanced around being an aoe, yet the stacks can only be procced with single target autoattacks! (And no one in their right minds is going to build a Runaan's on MF). This means that even if you do get off a full channel at the start of a fight, your stacks are going to fall off of your priority targets before you can finish burning through the frontline. It's kind of a conflicting bit of design imo.
I see two good solutions for this. The first, and most optimal IMO, is to put a base upfront AD ratio on MF's Ultimate so that having a successful lane phase can actually transition into a strong midgame. Immobile ADCs are already the hardest thing to play in solo queue; even with MF it just isn't feasible to bank on having a great lane phase and nothing else. Even if it's just 20-30% (though ideally around 40%), SOMETHING to actually put down damage while you are applying the stacks for follow up is important. ADCs need to always be doing damage or they are worthless, so standing around NOT dealing damage, but only preparing to do damage, really isn't an option. The second and less desirable option is to AT LEAST give MF the ability to follow-up on her ultimate's ideal use case, and keep stacks on all affected enemies for as long as she is keeping stacks on one with her autos. That way stacks don't fall off of carries while you are fighting tanks, which as an immobile ADC, you do not have the luxury of ignoring. Ever.
Anyway I'd be interested in hearing what the guy in charge of her "rework" thinks about her current state, as well as the design decisions that have led her to this point.