It doesn't scale with Spell Power, but Lifeblood does heals a bit more to Paladins if they have the Talent(s) [Divinity]from what I noticed. And it also heals a bit more for Warlocks.
It heals more for locks cause of Demon Armor (increasing the amount of health generated by spells and effects by 20%) not sure why for pallys though, maybe ret aura... idk i dont have a pally =)