At lower levels your characters don't have all of their tools yet.
That is the other factor that is hard at the moment.

Thunderstorm, is a knockback effect which also deals damage.
I believe mine is on a key like =.
The key is set up for a round robin effect, as in press 1 = shaman 1, press 2 = shaman 2, etc.
I've also made a few mapped keys, with Alt & =, Shift & =, and Ctrl & = as the hotkeys; each of these sends = to all the windows.
So I can press = once or twice, as needed as a round-robin effect.
But if you have a melee who you can kill, pressing it with a modifier will have all shammies fire it off.
If you press it in rapid succession, you will also frequently boot someone much further away then normal.

Some enemies are immune to knockback, be it from Pillars of Frost (DK) (pretty sure that's the knockback immunity move; they have one anyway) or a Warrior doing Bladestorm.
You can try to spread out so they're only hitting one of your toons.
You can also just heal through it, and not bother moving.
Either way, you'd likely drop 4/5x Magma Totems, so the melee is taking damage from multiple sources.

You'll have Earthbind Totem eventually, and talented this is a brief root followed by a snare effect.

You could set up a round-robin effect if you wanted.
It could be Thunderstorm (on A), Earthbind (on B), Frost Shock (on C) and then just advance the abilities for each subsequent press.