Thanks whityF0x for the response! Yes I just looked over the theory again and your right , because the amount deducted of Last whisper before the Debuff of Black Cleaver would be superior then if you have both so you are right! I hadn't done maths in a while. Yes the runes don't give much of each but do you mean I should be more constant? Like take more of the same type? I gonna think this out.... I'm thinking of replacing Last Whisper with Frozen Mallet, the slow on it is amazing ( or any other item that provides a slow). But do you have any positive feedback this being my first guide?

Your paragraph about Last whisper is actually wrong Percentage reduction is applied after flat armor reduction so it would be .

Malph 300 armor - 45 fro BC = 255
then Lw would be applied : 255 * 0,4 = 102 // 255 - 102 = 153

So Black Cleaver actually makes Last Whisper less effective ;) so dont buy both.

And i actually dont like ur rune choice.
Your Glyphs give 5,04 % higher crit dmg //
lets say we got IE at lvl 18 u got only with IE 188 dmg crit = 470
470 *0,05 = 23,5 thats nearly nothing :)
get some magic resist or Cdr that would be better.

And why would u want to Lane with Master Yi? :D