You just need to have it mapped (or not mapped) so that you aren't auto-assisting and casting with all of your guys at once.
There's a few different ways people like to do crowd control. One is to pre-target the mobs with your characters, and set the /focus target. Then you make your CC macro like
/cast [target=focus] MyCCSpell
And then it doesn't matter if you leave that key auto-assisting and broadcasting, because the spell itself will only cast on each guy's focus target.
You can also do a round-robin style and let it use the FTL targeting. With this method, you target a mob with your main and then press your round-robin CC hotkey, and one of your CC-capable guys will cast his spell on your target. Ualaa's ISBoxer guide has examples of how to do Round-Robin --
http://isboxer.com/index.php/component/ ... oxer-guide scroll down to part "6 Keymaps" and it's "Example E - How to Stagger Tremors (or anything else)". In a nutshell, the hotkeys generated by the wizard are single-step and configured to send the key to everyone, and to round-robin you make it multi-step, and configure it to send the key to one character at a time.