There is nothing wrong with Leech being an effective talent. The trouble is it's disproportionately powerful compared to many others. Why would I take a talent like Sidestep that gives a meager 10% chance to evade when I can choose to simply out-heal enemy attacks with Leech? Also with the recent patch preventing the seller of secrets from selling multiple stat/skill books it is clear that Larian does indeed care about balance, otherwise they would have let it be.
