Healing Units- A Must Have

All the races have at least one type of structure or person who can heal others. For example, the Humans have the Priests, the Orcs have the Witch Doctor, the Nightelves have their Keeper of the Grove/ Druid of the Claw/Moonwells and the Undead have the Blight/Statues. Also, some units have the ability to hell themselves by burrowing, turning to stone, etc, at an accelerated rate, and all units slowly heal themselves.

These units/structures are a must have, as they will heal any troops they see, especially when set on auto cast (right clicking the icon so there is a little gold sparkle around it) and can easily change the direction of any battle.