IMO Gundrak is the easiest Heroic for tank + 4 shaman. See the video I made on fighting the gundrak bosses to get ideas on where to position, what to do, etc:

http://www.vonderbecke.net/files/wow...rak-Bosses.wmv

The key to the second fight (elemental boss) is 4 healing stream totems and a nature resist. The rest of the bosses are quite easy, and the last boss is only tough if your tank is undergeared which yours isn't. Good luck and let us know how it goes!