The easy answer is:
-- Pally will Consecrate.
-- Shammy will drop a Magma Totem.
-- Mage will Arcane Explosion.
-- Druid will Starfall.
-- Shadow Priest will Mind Sear or Holy Nova.

As far as I know, only the Mage and Druid have different options.
The mage can also Blizzard while the Druid can also Hurricane.

Keyclone does support mouse broadcasting, there's a hotkey to toggle it on or off.
You can also set it (latest version) to be on for a single (the next) click.

Ellay had a post a couple of months ago, which I quoted part of today.
Where you /Script SetView(2);SetView(2) to be looking down at your toon.
Go into keybinds and bind view 2, to be looking down from zoomed in close.
Then the commands were: /script SetBinding(";", "CAMERAORSELECTORMOVE") and /script SaveBindings(1). If you want a key other then semi-colon, change the first Script.

Then you make your macro:
#show Blizzard
/Script SetView(2);SetView(2)
/Cast blizzard

Do the same for Hurricane.

By setting the view in advance and saving it. And then running a macro which changes your view to the saved view, it doesn't really matter where the mouse is clicked, it will be over your toons - which you want, so the pally can consecrate and holy shield for threat. The " ; " key will simulate a mouse click.

Honestly, the first option is a lot easier, but broadcasting is ok with keyclone and the set view is a third option.