Somebody explain miss fortune to me

So she's a adc, adcs are supposed to kill tanks but her current route (at least what I can make out of) is lethality to boost her abilities Q and R, even death fire as a mastery. So doesn't this mean that she'll only be good while the top laner/jungler/support aren't building armour items yet? Seems like she won't do a good job at tank killing unless im missing something.

Also is it possible to build hybrid on her? Like dusk blade, ghostblade, rpd, IE and deaths dance. Or are you still better off with the armour shredding build?