since you mentioned [target=targettarget] let me describe that's going on.

You use this on all your slaves. this assumes that your slaves are targeting your main. if your slave is targeting your main, then thats all your slaves will see. your main. it will not change targets unless your spell requires it. keep your slaves targeting your main character always.

[target=targettarget] basically tells your slaves to cast a spell on your target's (main) target. if your main is targetting a mob, then your slaves will attach whatever your main is targeting.

since you can really only target from one screen, using this method to do battle is a lot simpler. you cannot target the same thing from each slave independently unless the conditions are right. and usually, the conditions are never right (all slaves are in targeting range of the mob; only one mob). so use your main account to target, and have everyone target what your main is targeting. thats basically how this works.