The Jungle item and BORK deals %HP damage, which cleaves through Tanks while providing much needed Attack Speed and Lifesteal.The Black Cleaver reduces armor, which is absolutely devastating against tanks. As Master Yi is prone to disables, Merc Treads is essential to reducing Stun/Root time, while providing MR.Frozen Mallet (IMHO) is quite good, as it allows you to stick to your target, while providing much needed HP.