If you bind something to Control Up, and something else to Alt Up, and something else to Control + Alt + Up, then wow will look at these as separate commands.

Each will do what it is bound to do.

If nothing is bound to Control + Alt + Up, then that combination will attempt to execute both Control + Up and Alt + Up.

By binding the combinations which would normally do something, to a key which does nothing instead, you're forcing the game to do nothing on the combinations of your choice.



Personally, I think its a lot easier to have main tank.
Either unbind WASD on the other toons, or add them to the "Do Not Pass" list (sometimes called a Black List).
Then unbind the arrow keys on the main tank toon.
This gets you a way to move the main guy only, as well as a way to move the slaves as a group.



With InnerSpace, via ISBoxer Toolkit, you can accomplish this easily with keymaps.
Basically, if WASD aren't in any keymaps, then they are not broadcast to the other windows.
So by doing nothing, you can move the main via the keyboard without moving the slaves.

Then you create a keymap which has up arrow as the trigger key.
Select "all without current window" as the target group.
And pick the up arrow as the keybinding which is sent.

Repeat for each arrow key.

Then, no matter what toon you're on, WASD moves only that toon.
And the arrow keys move the slaves without moving the main/hot character.