You keep pressing the button that makes him cast, 1 button press, 1 action. Having multiple spellcasts on one toon on one keystroke takes you down the path towards automation and banning. You can stack actions like triggering trinkets or instant casts that don't trigger a cooldown (like a mage's PoM), but you can't push once and "cast this spell every time the cooldown is up until mob croaks". That's automation, and bad mojo.

I was thinking your issue with having to press 2 was a slight delay that can happen when slaves are picking up the main's target, they don't cast if they don't have a target, and there can be a slight delay in them acquiring it. A way to test it with that [] setup mentioned above is to target one mob and have hte main target a different named mob and hit your macro, then see which mob your slave casts on if any.

Again, still very much a noob myself, could be wrong, but the forum has been a big help to me, so I try to help back, even at risk of talking out my fifth point of contact.

Since you've already set your focus to the warrior, the macro with the target=focustarget will accomplish the same as the /target focus and /assist portions of your big button, the /stopcasting may or not play a role.