I've run into quite a few very powerful builds that rely on having high lifesteal from their items to heal through any damage thrown at them. But besides the anti healing items, which I feel should be more for countering actual healers, and apply a debuff to the opponent, there's nothing to really counter this. I would have expected there to be (and would like for there to be) a passive or active item and associated buff that makes you less susceptible to lifesteal, so that if you're in a 1v1 against someone with a heavy lifesteal build they'll struggle to keep themselves alive off of you, or in a teamfight they wont benefit as much from your presence. This is more of a late game purchase since it's to counter bulds that have multiple high tier lifesteal items, so it'd probably be expensive and since it's way more specialized than something like toxic bullets, healbane, or decay(and maybe more expensive) it'd need to be more powerful in the specific situation it's useful in.