Within warcraft, there's a section in the interface.

I think you can enable that any spell clicked/pressed with Alt targets yourself.
But pressing it without Alt and it acts normally.

If you want to use Alt conditionals in your macro's you'd want to be sure this is disabled.
Let your conditionals determine the target, rather then Alt always targeting the caster.

If that's not it, I'm not really sure.

With two toons, you could easily have one as the defacto healer.
Two macro's. Macro 1 is for Toon 1, and Macro 2 is for Toon 2.
A normal press is only Toon 2 casting, while a (pick a mod...or just use /cast [mod, target=]... has both toons heal.






If you're playing shammies and nothing else..
Frost Shock is your snare (along with Earthbind Totem) for keeping range.
Earth Shock is your biggest single instant cast.
Flame Shock is your most damage from a single shock over time (highest damage per cast shock).
Wind Shock is your interrupt.

There will be situations where you want one or the other.
There aren't really all that many keys you'll use with just the one class.

Lightning, Chain Lightning, Flame Shock, Lava Burst... for DPS
Earth Shock, Frost Shock, Wind Shock... situational use.
Totem stomp, all drop or sequential drop: Groundings, Healing Stream, Fire Nova, Earth Bind, Fire Elemental.
Purge, Heroism, Elemental Mastery, Hex, Totemic Recall.

Your most used keys will be on the keybinds easiest to access.
A lot of these you don't get until 70th, 75th or 80th anyway.
Easy to adapt your system over time, as you get new tools or your needs change.