Miss Fortune is underpowered and needs buffs...
She does no damage and lethality is bad on her, she needs alteast 150% damage increase on Q and her R should last way longer because there is no teamfight potential with it since you can just walk out. We also need more base HP regen and more base mana since your mana is empty after casting Q 10 times... She is unplayable now.
as your first 2 items gives you a 56% - 57% chance to win. Obviously you are doing it wrong and need to git gud. Secondly, crit builds on MF are fine as well, so it's not like she doesn't have a fallback option.