Hiyo!
I've come across a bit of grumbling about Mastermind pets in early-level PUGs, and thought maybe I ought to share some ancient wisdom somewhere. None of this is likely new to any experienced Mastermind player - and there are good resources out there for more fine control; but if you're just starting out or - like me - just plain lazy, these three binds I've been using since pretty much the inception of the AT'll do ya for most content.
You can change these to whatever keys work best for ya - or make macros, even! I play with one hand on WASD and the other on the mouse, so I keep everything pretty close together. /bind e "petcom_all follow def"
More than just the button for Bodyguard, this also functions as The Almighty Reset Button - with a bit of hammering. This makes it probably my most-used key. Pets chasing after a runner and threatening to face-pull a whole new pack? Mash this a few times and they'll drop target to return to you. It's important to note that this isn't a hard reset. Just as you can interrupt their actions, the order itself can be interrupted by anything that switches their focus priority - so, basically, mash it and keep mashing it until they've stopped doing whatever it is you don't want them to do. /bind q "petcom_all att agg"
The Focus Fire button! This is great for ranged pets, but also good in combination with the third bind. There's really not a whole lot to say about this one on its own. If your pets are attacking something you don't want them to attack, this'll put them back on track.
/bind t "petcom_all goto agg"
A very underrated button! This one has all kinds of uses; but I mostly use it to move melee pets into melee range - then follow up with 'q' to get them on target. This mostly negates melee pets getting stuck outside of melee range spamming their ranged attacks; though they do sometimes find a way to do so regardless. You can also use this to put ranged pets with cones into a good position for hitting the most targets with said cones. Sometimes it's also fun to just leave 'em somewhere to intercept and ambush - especially if you have lots of traps set out nearby. You could also use passive instead of aggressive, since using the focus-fire button will switch them to aggressive anyway. You can also use this to move them out of things like caltrops and burn patches - though they're as likely as not to just run right back into them once they resume attacking, if they're melee.
Basically, managing pets is like managing a bunch of eager puppies - they like to hyper-focus on one 'priority' at a time and you're really just there to change what that priority is by shouting at them until they finally decide to stop ignoring you; which generally doesn't take much - or maybe less than it used to?