I received some useful feedback on G+ from my previous post about the challenges of an RPG properly set in Middle Earth, specifically on the healing side of things.
One of the main points I hadn't really considered is that in both in The Hobbit and Lord of the Rings the fatality rate, and even the injury rate, from some fairly hairy situations is pretty low. Bilbo is knocked out and misses the Battle of the Five Armies, Frodo is injured on Weathertop and Eowyn by the Witch King, but otherwise characters are either fine or dead. So, we have 'a large dose of "don't be a wimp, carry on anyway"' (thank you +Jane Williams), perhaps a mechanic as per Heroes Against Darkness where characters can recharge significantly during or after a battle.
There are also plenty of the things I had considered - herbal cures, the "orc draught" and various other pieces of mystical healing, especially by Aragorn and various elves. The internet being what it is, there's good documentation on Wikipedia (of course) but also stacks to think about in a long article by Tinw.
So, I think that characters can be made fairly resiliant, although the challenge as always will be keeping some of the mystery and magic in the mechanics.