Earth Ponies, Pegasi, Unicorns, and Health [/overanalysis]

Disclaimer: This may or may not be a tour de force.

Anywho, so a while back, I'd written this fanfic (not linking due to TL-DR;) in which at one point, I maintain that only Luna and Celestia can use healing magic. Someone comments and points out that unicorns could branch out into various areas of magic (kinda like Final Fantasy's Blue Mage, Black Mage, White Mage, etc).

It kind of makes sense, though for a while, I wondered: If unicorns could wield healing magic, what the heck would be the point of hospitals? Or even alchemy, like with Zecora? So I've been thinking about how that would work without making the magic world broken, and what I've got so far is this:

• Way back when, all three tribes lived relatively separately (if Hearth's Warming Eve is to be believed).

• Earth Ponies, being confined to the ground and unable to manipulate anything with magic or wings, tended to have greater difficulty in keeping areas clean. In addition, they needed to interact more often with one another. As a result, they tended to get sick more often than unicorns or pegasi.

• On the other hand, because they were so often subject to disease, those who survived developed strong immune systems and overall resistance. They also saw the need to have potent medicines handy. Thanks to their already profound knowledge of the earth and growing things, they were able to develop alchemy, using herbs and potions to handle illness.

• They could not, however, so easily manage bodily injury (broken bones, lacerations, etc). This is where the unicorns come in. Using their healing magic, they're able to more efficiently close wounds and speed up the body's regeneration. If you want to take it a step further into RPG territory, they're able to "restore HP", curing damage.

• However, in the distant past, through a combination of living in rather sterile mountain castles and cleaning through magic, unicorns were not very strong against disease when they contracted something. As a result, through joining forces with the earth ponies, they were able to procure medicines to prevent disease. In exchange, they can heal earth pony injuries.

• Pegasi... are not well-gifted with medicine. Normally, they don't have to be. Disease? They tend to live in the sky, in great big open spaces. They can also fly around quite a bit. Diseases can have difficulty spreading in that manner. (There's also the manner of sanitation, as they can easily leave refuse on the ground below.) As for physical injuries, they are quite resilient, able to crash many times before they so much as bend a wing.

• However, as we saw in today's episode, when they DO get sick... diseases spread like wildfire, taking down quite a large number of Rainbow's pegasus force. So, while they are physically resilient, and do not catch diseases often - when they DO catch something, there can be devastating results.

In conclusion: