First of all, I searched first for "Balinda" "AV exploit" etc.. and came back with nothing, if this does happen to be a report please inform me and i'll delete the thread.
Earlier today when I was busy farming AV because I have nothing better to do today, I noticed something hitting me while I was tanking Balinda, so I looked about with my camera and saw a hunter standing on a "flag" inside Balinda's room attacking me. After we killed her and ranged DPS killed the hunter, I staying in Balinda's room until I figured out how they did it (it didn't take long just trail and error from jumping).
A few hours later, still farming AV I got really bored so I decided to take screen shots of how to get up there for any alliance that want to get in Balinda's room and slow down horde.
First of all, enter Balinda's room on the left (probably works on the right too, and maybe the third flag behind her, I just haven't tried).
Secondly, go near the flag, but inbetween the weapon racks to the left of it.
After that, jump up onto the little ledge between the weapon racks:
Once up there, jump, slightly to the right untill you get ontop of the weapon rack like shown in this next picture, then walk slightly foward untill you are kind of in the middle of the rack:
Once there, jump forward onto the metal rim on the flag:
(I aware I am not in the middle of the rack, didn't make it that jump xD)
Once you make the jump, face a 45 degree angle away from the wall (approx) and start jumping then tapping "w" or whatever you use to move forward untill you reach the top:
Once you are here, most likely the melee horde are going to be where the dead Balinda is on my next pic, so fire away!
Good luck with this and have fun untill Blizzard (possibly) decide to put invisible walls or something there to stop you getting up! -.-
Edit: Sigh pics aren't working already, i'll sort it out in a sec, bare with me.
Edit 2: Working now xD
Edit 3: :O First pic is missing! Doesn't matter though as you will see where I mean from the other pics.