It amazes me that anyone at riot could ever think this was OK and let it out of the PBE. Miss fortune's ult is so stupidly broken that its just laughable.
As an adc, her ult's slow is way too powerful and makes getting away almost impossible, which means that half the time you will absorb half your health in damage at level 6, with no scaling. That's just beyond dumb.
AP miss fotrune; well if you don't think this is OP you clearly haven't played against it. With the right itemization she has perma slows and takes out half a squishies HP with her E, and instantly locks down and kills the entire team with her ult. I played against her as riven, and couldn't even come close to catching her because of all her slowing BS.
Seriously, her base damage on her ult is absolutely stupid, and her slows give her more CC than some supports. She just ruins the game and makes it almost not worth trying if you are against her.