is lifesteal overly countered by armor stacking?

Life steal is a very inconsistent stat depending on who you are fighting. When going from healing off a minion, don't expect that same amount of healing to come even close when fighting the enemy tank like say sejuani.

Is armor overly effective vs life steal combined with how effective it is vs physical damage? Armor pen got hit but lifesteal didn't change. Why not do something similar to wota except instead of ignoring all their armor only a portion of their bonus armor.

In turn I think a cool rework for thornmail could involve someway to reduce an enemy's ability to life steal off you.

Maybe give the lifesteal quints essences ignore bonus armor.

I find when you see tank , tank , tank etc They will often stack armor. An improvement to lifesteal's performance against such champions could give fighters/assassins (less likely to want to build ) a better chance of making the most out of the lifesteal they depend on to survive. The rewards aren't quite worth the risk atm. While going tank is always reliable.