Have any other mages noticed that their mirror images are aggroing mobs that are not supposed to be involved in 5 man boss encounters? I ask because in my five man dungeon group we run two mages and on fights like Beauty in H-BRC Runty will not engage in the fight until one of the two mages throws up their mirror images. Same with the last boss in this instance, if we do not clear all the trash "near" the boss, as soon as images go up BAM, a pack of trash from 100 yards away comes into the fray. In raid encounters, we experienced the same in 10m Bastion, we would pull one set of the orb mage trash into the hall before their spawn points, cast images to absorb some of the nasty channeled spells and BOOM, the pack from across engaged as well.
I immediately thought of Faxmonkey's video "Stupid Mage Tricks: WotLK Edition" (easy to find still). At around 11:00 he explains
This bug is still live and it applies inside instances, even if you re-zone. In particular, if you wipe due to a pack of trash adding, return to the instance, and then cast MI within LoS of that pack then the pack will aggro immediately.
Damage a mob and then reset it. From then on, anytime you cast Mirror Images within sight of that mob it will instantly aggro -- no matter how far away it is.
The room before Ozruk in Stonecore has those non-elite sentries that try to call adds and it's easy to keep LoS with all the trash when you engage Ozruk. The last room in BRC definitely offers line of sight from the bosses to the trash pack and/or Runty, but I can't explain why either aggroed for the first time. The bombing run in Grim Batol does not appear to put you on the targets' threat tables, otherwise your first MI would bring the whole zone down on you. I don't understand what happened to the trash packs in Twilight Bastion either.
This bug does not cause MI to actually shoot at the affected mobs, rather it instantly aggroes all of them. The story in post 17 definitely is an experience with this bug, but I still can't explain why they aggroed to Triumphet the first time. My images have been on their best behavior since 4.0 but I've been running as frost, and they are still at least a little responsive to pet commands while your elemental is out. Do you ever have MI troubles as frost, or is it only when arc/fire? Does your party use sap, soothe, or anything else that might put you on a threat list without forcing aggro or combat?