its not a waste of mana when the critical ones you want always down are cast first ie have the first shammy cast totem of wrath and the second cast mana spring or whatever on your first click - the macro needs to be different per toon:

Shammy One:
/castsequence reset=7 Mana Spring Totem,Tremor Totem,Grace of Air Totem,Searing Totem

Shammy Two:
/castsequence reset=7 Totem of Wrath, Healing Stream Totem, Stoneskin totem....... or wahtever you want

I def wouldn't say its a waste of mana esp if you logicaly spread out what you are casting with each toon ie since your lvl'ing you may want to stagger Stoneclaw Totem so if needed you could have two out within 30 seconds basicly figure out what would help you the most and there isn't any rule that you have to hit the macro four times if you don't need it (hence why it resets every seven seconds to go back to your most important totems) also you may want to create two seperate totem macros and have one button for buff type totems and a second for pvp or questing where you can have even more control over what is being dropped without needing to devote a ton of buttons to the cause