On all of the slaves (main too, if you can stand it), enable (in interface - mouse options) "click to move".

Also have a hotkey (in keybinds) for "interact with target".

Interact range is 4x or 5x further away then follow range.
The default option for a hostile target is to run towards it and melee it to death.

Ideally, you wait until your group is in casting range.
And then press down arrow, which breaks the movement.

Now you're spread out, for reduced AoE vulnerability.
And are facing the target on each toon.