You know you can stop whining, and just solve the problem yourself.
You don't need to stack items. A small amount of resistance goes a long way for you. Especially when an item gives you a passive that is infinitely helpful for what you are trying to do. It's generally beneficial for you to sacrifice some small amount of damage, if it means you can stay alive longer. Because then, you'll be pushing out MORE damage. Why the hell do you think some ADCs are just so hard to kill? Those items like ninja tabis, cloth shirts, guardian angel, blade of the ruined king,
Also where are you getting 800 in your math? No amount of life steal will even get you that much. The healing is calculated from damage after reduction. While life steal is stacked additively, ADs have only three items that they can fully abuse, and their prices are in the upper 3000s with each one of them being a situational pick. If you did get all three of them, you're getting 42% life steal, but very low damage. If you're lucky enough to crit you can probably expect to see... maybe 100-125 out of it?