No this isn't a rant, this is a story of my own stupidity of a lesson I learned the hard way.
My story starts off in AV. I came in late so there was no way for me to get past the oncoming horde so my best bet was to play on D until they got to Vaan because they were at the bottleneck point. So I sat on D at SP graveyard waiting for the impending onslaught. I have my pet stay near the graveyard flag, turn her on aggressive, I run off to the distance, in an obscure yet adventageous spot to hide, shadowmeld and wait.
Fast forward a bit, AV is over, I hope on a gryphon from SW and head to BB. I am running to the boat dock, pass by a lvl 35 Tauren Shaman. Hmm why is the Booty Bay Bruiser red? Oh crap my pet is still on aggresive. Spirit run, don't summon my pet until the boat leaves, change to defensive.
Arrive at ratchet, catch a hippogryph to Gagdetzan. Run in the first gate, a level 70 Horde Hunter and Shaman are there trying to one shot people and run away. The Hunter hits me, takes half my life, some gaurds chase the hunter, 2 gaurds pound on me.. F#%k defensive, when I got hit, my pet used lightning breath before I even had a chance to press the follow button.
So now I know, keep my pet on passive all the damn time, not just in instances, but all the time.