Go for a team of 5. You don't have any reliance on anyone else then, and you know the capabilities of everyone in the instance

Either a tree or shammy healer would be good.
Solo play I prefer a tree healer. Wild growth is really good to keep everyone topped off, or to give them enough health to hold for another heal to hit.

Then again i did do some BC instances with one shammy resto and it worked rather well as well.
Earth shield helps to smooth out damage on the tank - and the shammies can all hit a heal on themselves or chain heal if things are looking bad.

Looking forward