User blog comment:Hidden Sniper/Mechanics that don't make sense to me - Part 1 Lifesteal/@comment-5266525-20130716082633

Lifesteal doesn't snowball, it scales with your DPS. It's not the same thing. Consequently, it's also why they removed it off of Doran's Blade, replacing it with flat healing, AND also partly why they nerfed armor.

And you aren't looking at this the right way. Lifesteal is only a factor if you are allowing him to attack in the first place. You could simply stop him from autoattacking you by CC'ing him or burst him down before he can do any significant damage.

This isn't even considering the fact that he SHOULDN'T be lifesteal tanking you until very late in the game when he has a near-full build.