If the enemy team has a vayne...

you may as well ff once she's got shiv and IE, because unless she's a complete shit tier player and just runs into the cc she is going to over power your team unless the score is like 20-2 or something, and even then she'll probably still be able to 2 shot your squishies and 2.3 shot your tanks. Unless you're rammus. Then you'll take 2.4... This champion is not healthy for this game.