I've done it succesfully with a team of 4 shamans (ilvl 213) and a Tank DK (ilvl 200)

my advice : stack healing totems (use the Earthliving weapon buff on each toon) + nature resist totem and keep them in the 10 yard range to benefit from healing wave bounce (which I didn't do on my video) and it will be allright

http://www.wegame.com/watch/GUNDRAK_HERO/