They take high-level player skill into account.
...Incidentally, given her power on SR, I would suspect MF to be higher than she is.
I also wonder: What is it about Darius that makes him so powerful? If he's the TT equivalent of Dominion Kassadin, why is that so?
Darius... It's pretty straight foward. He has all damage output, magic, true, physical.
He has a reset ultimate. He has a CC that grapples on to him.
A Q that does decent damage without even building damage.
A W that slows your attack speed and movement speed.
Pretty damn broken.