So I just got murdered by a ONE ITEM Lee at 400 hp. I guess my bad that I didn't expect he would just instantly pop a second healthbar.
His W interaction with Ravenous is absolutely disgusting. On W recast he gains lifesteal, 26% at max rank. With Ravenous and Doran's Blade he gets to 42% lifesteal. Ravenous active applies it at 150% potency, so 63%. It has a 100% AD ratio, so Lee Sin will heal for 63% of his AD per target.
This Lee has some 230 AD and hits 9 targets, which works out to +1300 HP. Lifesteal is based on post-mitigation damage so the actual number is a bit less. But I'll leave it up to redditors and the balance team to decide if a level 11 Lee Sin with Ravenous, Doran's Blade, Tunneler and 2 Long Swords should be able to instantly spawn a second healthbar by using Ravenous in the middle of a minion wave.