User blog comment:Hidden Sniper/Mechanics that don't make sense to me - Part 1 Lifesteal/@comment-2248060-20130717124315

Okay so unless the AD carry/person who you're hitting has nearly 100% lifesteal (pretty hard to get don't you think? Requires 6 BT's nearly fully stacked or you to be Sion) he shouldn't be out sustainting your damage even with Crits, 1k damage with a BT grants a whopping 180 health. Besides that point its the only way for most champions to heal up VS poke unless you have a sustain champion on your team, and if you don't well... you're probably gonna lose that.

Also carries are still squishy as hell, I don't know where you get your information from but buying lifesteal doesn't magically grant them 100 armor, Mr and 3k health or anything that can make them be considered squishier than a marshmallow, if you get kited to hell by an AD carry that is healing while running away from you then they just did their job properly man