Tarantio says:

The witch doctors and the demon hunters from these games have practically nothing in common but their names, though. I guess both witch doctors are stooped? I think health globes were a solution to the potion issue; that is to say, the game needed some knew way for all characters to heal themselves of damage that didn’t have the potential of trivializing things, like potions so often did in Diablo II. I admit, I was skeptical of the idea at first. From a flavor perspective, it’s weird for monsters to drop floating balls of health. I really like that they’re going to be tailoring different ways for health globes to drop during major boss fights, though- that sounds like exactly what the game needed to make boss fights more dynamic.