not putting any form of /assist or /focus blah blah in your pewpew macros fixes this, for pewpew keep targetting seperate from pewpewing so they only acquire a target once. Had an issue with this when I first started (usually main would die and id wipe due to 'wtf?' moments) until I realized I had no need to re-assist my focus on each spellcast when i could just hit one key each time I changed targets to do this form me. Now with CC it will be different but I dont have any in this group

*edit* and to make sure im targetting all the right things I have that button on my main bound to a raid icon. so when I hit 'T' on my keyboard (used T so I can change targets quickly in PvP, I also have the period on numpand bound to this as well since instances I rarely use my mouse) my main marks the target with a skull and the alts assist me for it and the moment I see the icon on the party-target windows in pitbull its time for /cast pewpew