Yea, most instances I run though, I have to throw a heal only on the roughest boss fights.

You'll notice on some fights I'll throw all of the grounding totems even though the boss is melee -- I actually do this since windfury totem is on the same button and I was too lazy to create a windfury-only button.

The Shammies won't actually be anywhere near mana efficient until they hit 60+ and get some more +crit gear and mp5. Seem to be doing ok so far, though. Since my main is the warrior, I can get impatient sometimes and forget to drink before bosses. :P