Do healing globes improve as you progress?
Yes and no. Health globes heal a percentage of your character's maximum health based on which type of health globe you pick up (Depends on the Size of the globe). The only way to get more than the percentage you're supposed to get is through items that increase the amount of health you get from health globes by X, abilities, or passives. You'll always gain more from them the more health you have, but otherwise you can only improve them with items, abilities, or passives.