if heartseeker strike does physical damage, that counts with armor penetration.
if it does magic damage, it counts with spell penetration.

new record from this build.... 32/7/15

last i heard it was. Ive also seen a difference too. If i buy a brutalizer or a BF sword, the damage is roughly the same. BF sword does beat it barely but 25 damage + 15 armor penetration from a brutalizer and +50 damage from a BF sword is roughly are roughly the same. its only like a 10 damage difference. which the difference between a BF sword and a brutalizer is like 450ish gold. which is the price of a long sword.

Im just saying that armor penetration is also factored with the x5 heatseeker. and since you get more armor penetration from marks and quient runes then ya do with their damage counterpart, armor penetration is the way to go

Reason for damage runes is Heartseaker Strike.... The x5 factor of it plays a big role, and I'm pretty sure it isn't effected by armor penetration.

good to see others agree :). however I looked at the math for damage and armor penetration (you can find a number of these post in the LOL forums), and Armor penetration actually develops more damage over all. Armor penetration even beats crit damage runes.

I have seen other pantheons use dorans blade from the start as well. it is a good starting item but it doesnt develop into anything which for me is a waste of gold. that 435 gold can be 5 min faster of getting a BF sword or speed up your brutalizer. If HP is your concern id much rather start with an elixir of fortitude which gives ya more HP and 20 damage. sure it only last for a few min but at level 1 its the best your going to get as far as damage and health.

My build is nearly exact to yours, and yes, it does work :D Only difference is that I go Doran's blade first and I use damage runes not armor penetration. (and perhaps 2 blood thirsters instead of infinity edge)