This is a trick I use on my Hunter which I discovered a while ago. I did not wish to put it in the "exploits" but it does not come off as an exploit to me, but who am I to judge?
When your party becomes mind controlled, your pet reverts to aggressive and will continue to beat on your party members. With this strategy, it makes them not attack unless attacked first.
This works on any boss that randomly mind controls, it will not work on Shaman totems since you do not directly control them, but it will work on mages ice elementals if they are summoned before the mind control and with warlock pets.
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Before the pull, move away from the hostile area you'll be fighting the boss in. For Blackheart, you'll need to move back a bit more, since he has a knockback. So assume 35ish yards and give him the "stay" command. When the fight starts, you'll see he has the "stay" command active. What this means, is when the monsters are slain he runs back to the spot he was told to stay. It ALSO means that when the party becomes mind controlled, your pet deaggros and runs back to the spot he was told to stay instead of attacking your party members. Since it's so far away from the other players, he sits there, passively, until the mind control ends at which point. He'll still be "staying" so you give him orders to attack, and repeat harmlessly.
You don't want to keep him too far out of range when you tell him to stay because he can despawn, which is not bad it just ends the stay command when you resummon him.
If this saves one Hunter/Warlock/Mage from getting yelled at, it's worth it. ^.~