There are a lot of software (or hardware) options as far as key broadcasting goes.

In addition to this Jamba is highly recommended.
It will have the slaves mimic a lot of choices the master makes if the window is open on each toon.
You can have the slaves take the same quest choices, or dialogue. Same or different rewards from quests.
Take the same Flight Path, if both have the Flight window open.

With "Click to Move" and "Interact with Target", its very easy to target the same thing as the main, without ever leaving the main's window.
The only time you "need" to be on the slaves window, is to herb/mine or accept trades or do their own mail.

Your spells and abilities, assisting and such are controlled by in-game macro's.
There are a variety of assist methods.
With two toons you could use assist, as mentioned earlier in the thread.

Alternatively:
You can have every toon focus the leader, and have a leader key for each toon.
Your macro's can be... /cast [target=focustarget] Spell Name.
Then any toon can lead as well as any other.

You can go with assist based off of targeting, search for the "No Focus Manifesto".
Basically each toon targets the leader, and casts at the leader's target.

You can go with promoting the active toon to party leader.
And then /cast [target=party1target] Spell Name.
This method requires paging action bars, and no longer works well in pvp's, but is very easy for PvE.

The FTL is harder to set up, but quite a bit stronger then other assist methods.
While leveling, I'd personally not do it, as the set up is involved for each spell.
Once you're 80 and have all your toys, its very strong.
Assist is determined by the window you click in, and is not dependent on Targeting, Focus or a Party leader.



In addition to your assist method, you have a few choices for the spells themselves.

You can go with /cast Spell Name.
You can go with a /castsequence Spell 1, Spell 2, Spell 3
You can go with a /castrandom Spell 1, Spell 1, Spell 2, Spell 3 (2 chances of spell 1, 1 chance each of Spell 2 or 3).

You can get extremely creative with "Click Castsequences", and manage multiple spells with variable refresh times on a single button spam.



Lots of options to explore.
For me the macro's and configuration to get something to work exactly as I'd like it to, is as good as the play.