Leech still heals you with Zombie if you get someone to hit that character with a weak weapon or bleeding ability. I sense an incoming nerf to Leech, though, because it basically makes you invulnerable to physical attacks if you have high enough armour because it heals every time a char gets hit unless in a fire.
The higher level earth spell Deadly Spores is also excellent for healing a Zombie char. I'd refrain from choosing Zombie at all on hard mode though.
