Some questions (that may or may not be important) to consider:
1. How do Aang's arrows glow when in the avatar state? Do the air-nomads know how to make 'spirit ink' or something? Also, those are some pretty big tattoos for a 12 year old. It must have hurt.
2. When Iroh was in the spirit world, did he speak with Avatar Roku? Roku seems to know how to guide Aang through his ordeal, but Iroh seems to know how to guide Zuko as well.
3. Can male waterbenders heal? I assume some can, but it has yet to show a male waterbender healing anyone. Also I'm guessing that at least one waterbender avatar who could heal has existed, which means others can probably heal when in the avatar state even though we have not seen it. But can an avatar from other nations besides the water tribe ever learn to heal outside of the avatar state?