Muramana, BotRK, Wit's End, Black Cleaver, Frozen Heart, Merc Treads

All of those items compliment each other, to make Vayne not only tanky but she never loses any damage. Warmogs and spirit Visage don't do much for you, they are just there giving you health and MR. Black Cleaver gives you almost as much health but it has armor shred as well. Frozen Heart gives you 100 armor and reduces the enemy attack speed by 15% but it also gives you a 20% cooldown, allowing you to have your ult up faster and the bonus mana makes the muramana hit harder. Merc Treads give you the MR and tenacity which reduces CC. Wit's End gives you magic resist and allows you to apply more muramana and BotRK hits which really brings the pain.

It's not just about being tanky, it's about being tanky with items that compliment each other, each having its own strengths while bolstering the other items in the build as well.