I go with whatever benifits me to kill stuff faster. Unfortunately for elemental shaman, there isn't a lot of low/mid level leather/mail gear that has spell damage or decent int. So I have been playing mainly in cloth gear with no tank. I have had no problems doing instances at the appropriate level even with no tank and the cloth gear. The thing that I find inportnat for any sucessful instance is preparation. Pull wisely and avoid CL if possible and use the stoneclaws/grounding to your advantage.