Luckily I read a post about it here when my doll was level 16. Saved all my skill points and threw them all in and added one more when I brought the doll to level 21. Best decision I have made in this game! (unlike Chain Shot, Cleave, Focus, etc.)
With Life Drain maxed, I use Rock Crabs and Sergeants like tonics! If my health is low and I am near one, I tap one killing it instantly and usually restoring my hp to full power. This actually doesn't make sense since at times I seem to restore more hp than the low-level enemy should have, but I'm not arguing about it.
